Stringed instrument

Abstract

A stringed instrument according to the present invention comprises a neck, a plurality of conductive frets that are arranged at intervals from each other along the neck, a plurality of conductive strings that can contact any of the plurality of frets, a plurality of drive coils that respectively correspond to the plurality of frets, a signal supply unit that sequentially supplies a drive signal to each of the plurality of drive coils, a feedback line that is connected to each of the plurality of frets, and a voltage detection unit that detects a first detection voltage between a first string of the plurality of strings and the feedback line during supply of the drive signal to each of the plurality of drive coils.

Description

string instruments

[0001] The present disclosure relates to stringed musical instruments.

[0002] Techniques for detecting the position of each string of a stringed instrument where a player has pressed down have been proposed. For example, Patent Document 1 discloses a technique for detecting the position of a string being pressed down by using coils installed at each fret on the surface of the neck of an electric stringed instrument. In the configuration of Patent Document 1, voltage pulses are sequentially supplied to each of a plurality of strings, and the pressed position is identified by detecting the induced voltage generated in each coil by the application of the voltage pulses.

[0003] Utility Model Application Publication No. 4-85394

[0004] In the configuration of Patent Document 1, a large current is generated in each string due to the supply of a voltage pulse. Therefore, the current in each string may affect the operation (pickup) that magnetically detects the vibrations generated in the strings when played. In consideration of the above, one aspect of the present disclosure aims to detect the finger position of a stringed instrument while suppressing the effect on the detection of string vibrations.

[0005] A stringed instrument according to one aspect of the present disclosure comprises a neck, a plurality of conductive frets arranged at intervals along the neck, a plurality of conductive strings that can contact any of the plurality of frets, a plurality of drive coils respectively installed at intervals between the plurality of frets, a signal supply unit that supplies a drive signal to each of the plurality of drive coils, a feedback line connected to a first string of the plurality of strings, and a voltage detection unit that detects a first detected voltage between the first string and the feedback line during the period in which the drive signal is supplied.

[0006] 5 is a plan view of an electric bass guitar according to a first embodiment; FIG. 6 is an explanatory diagram of the principle of detecting a pressed position; FIG. 6 is an explanatory diagram of the principle of detecting a pressed position; FIG. 7 is an explanatory diagram of the principle of detecting a pressed position; FIG. 7 is an enlarged plan view of a portion of the fingerboard; FIG. 8 is a plan view of the neck; FIG. 8 is a cross-sectional view taken along line VII-VII in FIG. 5; FIG. 9 is a cross-sectional view taken along line VIII-VIII in FIG. 5; FIG. 9 is an explanatory diagram of the relationship between each string and a feedback line in the first embodiment; FIG. 10 is an explanatory diagram of the relationship between each string and a feedback line in the second embodiment; FIG. 11 is a block diagram illustrating the configuration of a detection device; FIG. 12 is an explanatory diagram of the operation of a signal supply unit; FIG. 13 is a circuit diagram for supplying drive signals to each drive coil; FIG. 14 is a circuit diagram illustrating the configuration of a voltage detection unit; FIG. 15 is an explanatory diagram of a decrease in detected voltage due to pressing of multiple strings; FIG. 16 is an explanatory diagram of a reference voltage; FIG. 17 is an explanatory diagram of the differential voltage between the detected voltage and the reference voltage; and FIG. 18 is a transient response related to an amplifier; FIG. 19 is an explanatory diagram of the principle of detecting a pressed position in a third embodiment; FIG. 19 is an explanatory diagram of the principle of detecting a pressed position in the third embodiment; FIG. 19 is an explanatory diagram of the principle of detecting a pressed position in the third embodiment. FIG. 10 is a schematic diagram of detected data; FIG. 11 is a schematic diagram of temporal changes in the voltage of each string; FIG. 12 is a part of a flowchart of the string pressing analysis process; FIG. 13 is another part of the flowchart of the string pressing analysis process; FIG. 14 is a block diagram illustrating an example of the configuration of the signal output unit and the string pressing analysis unit in the fourth embodiment; FIG. 15 is a cross-sectional view showing the relationship between the connection unit and the frets in the fifth embodiment; FIG. 16 is a cross-sectional view of the neck in a modified example of the fifth embodiment; FIG. 17 is a cross-sectional view of the neck in a modified example of the fifth embodiment; FIG. 18 is a block diagram illustrating an example of the configuration of the signal supply unit in the modified example; FIG. 19 is a cross-sectional view of the neck in a modified example of the first embodiment.

[0007] A: First Embodiment Fig. 1 is a plan view of an electric bass guitar 100 in a first embodiment. The electric bass guitar 100 is a stringed instrument that includes a body 10, a neck 11, a fingerboard 12, a head 13, a plurality (N) of frets 14_1 to 14_N, five strings 15_1 to 15_5, and a detection device 30. The body 10 is a structure that supports each element of the electric bass guitar 100. In the following description, an X-axis and a Y-axis are assumed to be orthogonal to each other.

[0008] Each of the five strings 15_1 to 15_5 is a linear conductor including a first end E1 and a second end E2. The material of each string 15_m (m = 1 to 5) is arbitrary. The neck 11 is a long member extending along the Y-axis. That is, the Y-axis is an axis along the direction in which the neck 11 extends. The base end of the neck 11, located in the negative direction of the Y-axis, is fixed to the body 10. The head 13 is attached to the tip of the neck 11, located in the positive direction of the Y-axis. Five pegs 16 corresponding to the different strings 15_m are attached to the head 13. The first end E1 of each string 15_m is fixed to the peg 16. The body 10 is attached to a bridge 17 to which the second end E2 of each string 15_m is fixed.

[0009] The fingerboard 12 is a long, plate-like member attached to the neck 11. The fingerboard 12 is positioned between the five strings 15_1 to 15_5 and the neck 11. Each string 15_m faces the surface of the fingerboard 12 with a gap between them. N frets 14_1 to 14_N are conductive members attached to the surface of the fingerboard 12. Specifically, the N frets 14_1 to 14_N are arranged in the Y-axis direction with gaps between them. Each fret 14_n (n = 1 to N) is a long member extending in the X-axis direction across substantially the entire width of the fingerboard 12 and protruding from the surface of the fingerboard 12. Of the N frets 14_1 to 14_N, the fret 14_1 located at one end of the arrangement is closest to the head 13, and the fret 14_N located at the other end of the arrangement is closest to the bridge 17.

[0010] A nut 18 is installed at the end of the fingerboard 12 closest to the head 13. Five strings 15_1 to 15_5 are stretched with a predetermined tension between the nut 18 and the bridge 17. Specifically, the five strings 15_1 to 15_5 extend in the Y-axis direction at intervals along the X-axis. Any one of the five strings 15_1 to 15_5, 15_m1 (m1 = 1 to 5), is an example of the "first string," and another string 15_m2 (m2 = 1 to 5, m1 ≠ m2) is an example of the "second string." The nut 18 is formed, for example, from an insulating material; however, it may also be formed from a conductive material, as long as it does not come into contact with the feedback line 22, which will be described later.

[0011] Each of the five strings 15_1 to 15_5 is located at a distance from N frets 14_1 to 14_N when not pressed by the player. When pressed by the player, each string 15_m can come into contact with any of the N frets 14_1 to 14_N. Pressing a string is a performance operation in which each string 15_m is pressed toward the fingerboard 12. The player can press any position on the desired string 15_m within the range of the fingerboard 12.

[0012] A plurality of pickups 19 are installed on the body 10. Each pickup 19 detects vibrations generated in the strings 15_m by the performer's playing (specifically, by plucking the strings) and generates an acoustic signal corresponding to the vibrations. The acoustic signal generated by each pickup 19 is processed by an acoustic device (not shown), such as an amplifier, and then reproduced as sound waves.

[0013] The detection device 30 detects whether or not the player has pressed down on each of the five strings 15_1 to 15_5 and the position at which the string is pressed (hereinafter referred to as the "string pressing position"). Specifically, for example, one or more frets 14_n out of the N frets 14_1 to 14_N that have come into contact with the string 15_m due to the player's pressing are detected as the string pressing position for each string 15_m. Note that while FIG. 1 illustrates an example in which the detection device 30 is built into the body 10, the detection device 30 may also be configured separately from the electric bass 100 and connected to the electric bass 100.

[0014] 2 is an explanatory diagram of the principle of detecting the fingering position of any one string 15_m. The electric bass guitar 100 is equipped with N drive coils 21_1 to 21_N corresponding to different frets 14_n. Each drive coil 21_n is located between the adjacent frets 14_n and 14_n-1. As described above, N drive coils 21_1 to 21_N are installed at each interval between the N frets 14_1 to 14_N.

[0015] The feedback line 22 in FIG. 2 is a linear wiring including a first end Ea1 and a second end Ea2, extending in the Y-axis direction with a gap between it and each string 15_m. The first end Ea1 is the end of the feedback line 22 located in the positive direction of the Y-axis, and the second end Ea2 is the end of the feedback line 22 located in the negative direction of the Y-axis. The feedback line 22 is electrically connected to the string 15_m. Specifically, the feedback line 22 is connected to a portion of the string 15_m located in the positive direction of the Y-axis (i.e., closer to the tip of the neck 11) than the N frets 14_1 to 14_N. For example, the first end E1 of the string 15_m is connected to the feedback line 22. Therefore, the string 15_m and the feedback line 22 form a one-turn coil (hereinafter referred to as the "detection coil 28_m"). Furthermore, each of the N frets 14_1 to 14_N is electrically connected to the feedback line 22.

[0016] A drive signal D is sequentially supplied to each of the N drive coils 21_1 to 21_N in a time-division manner. The drive signal D is a periodic signal whose signal level fluctuates periodically. When a current flows through the drive coil 21_n (primary coil) in response to the supply of the drive signal D, mutual induction resulting from the magnetic field generated in the drive coil 21_n generates an electromotive force in the detection coil 28_m (secondary coil) formed by the string 15_m and the feedback wire 22. In the first embodiment, a detection voltage V_m between the string 15_m and the feedback wire 22 is detected, and the string-pressing position is determined based on the detection voltage V_m. The detection voltage V_m is the voltage between a second end E2 of the string 15_m, which is located in the negative direction of the Y axis relative to the N frets 14_1 to 14_N (i.e., closer to the base end of the neck 11), and a second end Ea2 of the feedback wire 22, which is located in the negative direction of the Y axis.

[0017] 3 and 4 show adjacent frets 14_n and 14_n-1 with a drive coil 21_n sandwiched therebetween. It is assumed that a drive signal D is supplied to the drive coil 21_n.

[0018] 3 , when the portion of string 15_m between frets 14_n-1 and 14_n-2 is pressed, fret 14_n-1, which is located in the positive direction of the Y axis relative to drive coil 21_n to be driven, comes into contact with string 15_m. Therefore, when drive signal D is supplied to drive coil 21_n, an electromotive force is generated in detection coil 28_m, which is formed by string 15_m, fret 14_n-1, and feedback line 22. Therefore, detection voltage V_m fluctuates periodically, just like drive signal D. Detection voltage V_m also fluctuates periodically when string 15_m is open.

[0019] 4 , when the portion of the string 15_m between the fret 14_n and the fret 14_n-1 is pressed, the fret 14_n located in the negative direction of the Y axis relative to the drive coil 21_n to be driven comes into contact with the string 15_m. Therefore, even if the drive signal D is supplied to the drive coil 21_n, the voltage of the detection coil 28_m (detection voltage V_m) does not substantially fluctuate.

[0020] As described above, the detected voltage V_m during the period when the drive signal D is supplied to each drive coil 21_n (the supply period T_n, described below) varies depending on the pressed position of the string 15_m. Therefore, the pressed position of the string 15_m can be identified using the detected voltage V_m when the drive signal D is sequentially supplied to each of the N drive coils 21_1 to 21_N. Note that when the string 15_m is released (when no position on the string 15_m is pressed), the detected voltage V_m fluctuates periodically.

[0021] As described above, in the first embodiment, mutual induction caused by the supply of drive signal D to drive coil 21_n generates an electromotive force in detection coil 28_m, which includes string 15_m and feedback line 22. Then, the pressed position of each string 15_m is identified by detecting detection voltage V_m between each string 15_m and feedback line 22. Therefore, compared to a configuration in which electromotive force is generated in drive coil 21_n by supplying drive signal D to string 15_m, the current flowing through string 15_m is reduced. With the above configuration, the presence and position of pressed strings 15_m can be detected quickly and accurately while minimizing the effect on the operation of pickup 19 in detecting vibrations generated in string 15_m due to playing.

[0022] Furthermore, in the first embodiment, as described above, the first end E1 of each string 15_m is connected to the first end Ea1 of the feedback line 22, and the voltage between the second end E2 of each string 15_m and the second end Ea2 of the feedback line 22 is detected as the detection voltage V_m. Therefore, contact of each string 15_m with any of the N frets 14_1 to 14_N can be detected across the entire area of ​​the neck 11 in the Y-axis direction.

[0023] Fig. 5 is an enlarged plan view of a portion of the fingerboard 12. Fig. 6 is a plan view of the neck 11 with the five strings 15_1 to 15_5 and fingerboard 12 removed from Fig. 5. As illustrated in Figs. 5 and 6, when viewed from a direction perpendicular to the surface of the fingerboard 12 (hereinafter referred to as "plan view"), a drive coil 21_n is installed between each fret 14_n and fret 14_n-1.

[0024] Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 5, and Fig. 8 is a cross-sectional view taken along line VIII-VIII in Fig. 5. As illustrated in Figs. 6 to 8, grooves 112 are formed on the surface of neck 11 facing fingerboard 12, and grooves 123 are formed on the surface of fingerboard 12 facing neck 11.

[0025] Groove 112 and groove 123 are elongated recesses extending along the Y-axis. A space surrounded by the inner surfaces of groove 112 and groove 123 (hereinafter referred to as "accommodation space Q") is formed between the neck 11 and the fingerboard 12. Accommodation space Q is an elongated space extending along the Y-axis across the entire area of ​​the neck 11 in the Y-axis direction. Note that accommodation space Q may be formed by only one of groove 112 and groove 123. In other words, one of groove 112 and groove 123 may be omitted.

[0026] The accommodation space Q accommodates a wiring board 20. That is, the wiring board 20 is placed between the neck 11 and the fingerboard 12. The wiring board 20 is a long, plate-like member that extends along the Y-axis across the entire area of ​​the neck 11 in the Y-axis direction. The wiring board 20 is a mounted component in which multiple wirings are formed on and inside an insulating substrate. For example, a multilayer board in which multiple insulating layers and multiple conductive layers are alternately stacked is used as the wiring board 20.

[0027] On the surface of the wiring board 20 facing the fingerboard 12 (hereinafter referred to as the "mounting surface 20a"), N driving coils 21_1 to 21_N, N connecting portions 24_1 to 24_N, a feedback line 22, and a reference line 23 are arranged. The feedback line 22 and the reference line 23 are wirings that extend in the Y-axis direction across the entire area of ​​the wiring board 20 in the Y-axis direction, and are formed, for example, as conductive patterns on the mounting surface 20a.

[0028] As described above, the feedback line 22 is a wire that extends linearly in the Y-axis direction between the first end Ea1 and the second end Ea2. The feedback line 22 is installed near the center of the mounting surface 20a of the wiring board 20 in the X-axis direction. In other words, the feedback line 22 extends along the center line of the wiring board 20. As can be seen from FIGS. 7 and 8 , the fingerboard 12 is located between each string 15_m and the feedback line 22.

[0029] The reference line 23 is a dummy string that does not directly contribute to the performance of the electric bass 100. Like the feedback line 22, the reference line 23 is a wire that extends linearly in the Y-axis direction. The reference line 23 is installed on the mounting surface 20a at a distance from the feedback line 22. Specifically, the reference line 23 is formed along the edge of the wiring board 20 that is located in the positive direction of the X-axis.

[0030] The N drive coils 21_1 to 21_N are arranged in the Y-axis direction at intervals from one another. As illustrated in FIGS. 6 and 7 , each drive coil 21_n is, for example, a chip coil mounted on the mounting surface 20a. Each drive coil 21_n is installed at the center of the wiring board 20 in the X-axis direction. Therefore, each drive coil 21_n overlaps the feedback line 22 in a plan view. Specifically, each drive coil 21_n is joined to the mounting surface 20a so as to straddle the feedback line 22. In other words, the N drive coils 21_1 to 21_N are positioned between the fingerboard 12 and the feedback line 22. With the above configuration, the N drive coils 21_1 to 21_N are not exposed to the outside of the electric bass guitar 100. Therefore, each drive coil 21_n can be installed while maintaining the appearance of the fingerboard 12.

[0031] 6, the N connection portions 24_1 to 24_N are arranged in the Y-axis direction at intervals. Specifically, each connection portion 24_n is disposed in the center of the wiring board 20 in the X-axis direction. Therefore, each connection portion 24_n overlaps the feedback line 22 in a plan view. Each connection portion 24_n is a connection terminal or metal fitting electrically connected to the feedback line 22.

[0032] Each of the N connection portions 24_1 to 24_N corresponds to a different fret 14_n. Each connection portion 24_n overlaps the corresponding fret 14_n in plan view. Therefore, each connection portion 24_n is located between the adjacent drive coils 21_n and 21_n-1.

[0033] As illustrated in FIG. 8 , each fret 14_n has a protrusion 141. The protrusion 141 protrudes from a portion of the fret 14_n extending in the X-axis direction toward the neck 11. On the other hand, a mounting hole 122 corresponding to each fret 14_n is formed in the fingerboard 12. Each mounting hole 122 is a through-hole that penetrates the fingerboard 12. The protrusion 141 of each fret 14_n penetrates the fingerboard 12 by being inserted into the mounting hole 122. The tip of the protrusion 141 of each fret 14_n is connected to the connection portion 24_n within the accommodation space Q. That is, each connection portion 24_n is connected to the protrusion 141 of the fret 14_n corresponding to the connection portion 24_n. Note that multiple protrusions 141 may be formed on one fret 14_n.

[0034] As explained above, each of the N frets 14_n is electrically connected to the feedback line 22 via the connection part 24_n corresponding to that fret 14_n. With the above configuration, each fret 14_n can be electrically connected to the feedback line 22 with a simple configuration that does not require wiring. On the other hand, the reference line 23 does not contact any of the N frets 14_1 to 14_N.

[0035] 9 is an explanatory diagram of the relationship between the five strings 15_1 to 15_5, the feedback line 22, and each drive coil 21_n. The five strings 15_1 to 15_5 are connected to one feedback line 22. Specifically, as described above, the end (first end E1) of each string 15_m located in the positive direction of the Y axis is connected to the end (first end Ea1) of the feedback line 22 located in the positive direction of the Y axis.

[0036] As described above, the first embodiment utilizes mutual induction between each drive coil 21_n and the detection coil 28_m including the string 15_m and the feedback line 22. That is, the magnetic flux generated in each drive coil 21_n by the supply of the drive signal D interlinks with the detection coil 28_m including the string 15_m and the feedback line 22.

[0037] As described above, the magnetic flux generated in one drive coil 21_n interlinks with the detection coils 28_m, which include each of the five strings 15_1 to 15_5. In other words, the drive coil 21_n is shared to detect the fingering position of each of the five strings 15_1 to 15_5. Therefore, compared to a configuration in which a drive coil 21_n is individually installed for each string 15_m, the configuration of the electric bass guitar 100 can be simplified by reducing the number of drive coils 21_n. Note that the detection coil 28_m1 is an example of a "first detection coil," and the detection coil 28_m2 is an example of a "second detection coil."

[0038] 10 is a schematic diagram of an embodiment (hereinafter referred to as the "second embodiment") in which a separate feedback line 22 is provided for each of the five strings 15_1 to 15_5. A detection coil 28_m is formed by connecting each string 15_m to a separate feedback line 22. That is, in the second embodiment, five detection coils 28_m corresponding to different strings 15_m are arranged side by side at intervals in the X-axis direction. In the first embodiment, the five strings 15_1 to 15_5 are connected to the feedback lines 22, and therefore the configuration of the electric bass guitar 100 can be simplified compared to the second embodiment by reducing the number of feedback lines 22.

[0039] In the second embodiment, each drive coil 21_n needs to be formed long in the X-axis direction so that the magnetic flux of each drive coil 21_n interlinks with five detection coils 28_m. Specifically, for example, the drive coil 21_n needs to have a dimension that spans the entire width of the fingerboard 12.

[0040] In contrast to the second embodiment, in the first embodiment, five strings 15_1 to 15_5 are connected to a single feedback line 22. In the above configuration, as can be seen from FIG. 9 , the five detection coils 28_m corresponding to different strings 15_m are in close proximity to one another near the feedback line 22. Therefore, even if the dimension of the drive coil 21_n in the X-axis direction is small, it is possible to link the magnetic flux of the drive coil 21_n to the five detection coils 28_m. In other words, the size of the drive coil 21_n required to magnetically couple the detection coil 28_m corresponding to each string 15_m to each drive coil 21_n can be reduced.

[0041] In the above description, the second embodiment has been illustrated for convenience in comparison with the first embodiment, but the second embodiment is not excluded from the scope of the present disclosure. The configuration of the second embodiment is naturally included within the scope of the present disclosure. That is, in the present disclosure, a feedback line 22 may be individually installed for each of the five strings 15_1 to 15_5, and a detection coil 28_m may be individually configured for each string 15_m by connecting each string 15_m to each feedback line 22. Note that the second embodiment is similar to the first embodiment except for the configuration in which the feedback line 22 is installed for each string 15_m.

[0042] 11 is a block diagram illustrating the configuration of the detection device 30. The detection device 30 includes a signal supply unit 40, a voltage detection unit 50, and a string pressing analysis unit 60A. The signal supply unit 40 supplies a drive signal D to each of the N drive coils 21_1 to 21_N.

[0043] 12 is an explanatory diagram of the operation of supplying a drive signal D to each drive coil 21_n. As illustrated in FIG. 12, N supply periods T_1 to T_N on the time axis constitute one cycle, and the operation of supplying a drive signal D to each of the N drive coils 21_1 to 21_N is repeated. Each supply period T_n has a predetermined length. In one supply period T_n, a drive signal D is supplied to one drive coil 21_n. In other words, the drive signal D is supplied to each of the N drive coils 21_1 to 21_N in a time-division manner for each supply period T_n.

[0044] 13 is a circuit diagram of a configuration for supplying a drive signal D to one drive coil 21_n among the N drive coils 21_1 to 21_N. The configuration of FIG. 13 is installed for each of the N drive coils 21_1 to 21_N.

[0045] The signal supply unit 40 includes N drive circuits 41_1 to 41_N corresponding to different drive coils 21_n. Each drive circuit 41_n outputs a drive signal D0 whose voltage fluctuates periodically. The drive circuit 41_n is, for example, an inverter circuit configured by a logic circuit.

[0046] The drive signal D0 is a square wave whose voltage fluctuates at a frequency F0. The frequency F0 is within a predetermined range (e.g., 1.5 MHz or more and 2.5 MHz or less) including, for example, 2 MHz. For example, the frequency F0 is set to a value of about 2.3 MHz. The voltage amplitude of the drive signal D0 is, for example, 5 Vp-p (peak-to-peak).

[0047] The output terminal of the drive circuit 41_n and one end of the drive coil 21_n are connected by a signal line 42. The other end of each drive coil 21_n is connected to a common line 47. The signal line 42 and the common line 47 are wires formed on the wiring board 20. The common line 47 is grounded.

[0048] A capacitor 43, a low-pass filter 44, a resistive element 45, and a capacitor 46 are installed on the signal line 42. The capacitor 43 removes the DC component of the drive signal D. The low-pass filter 44 suppresses the high-frequency component of the drive signal D. The drive coil 21_n, the resistive element 45, and the capacitor 46 form a resonant circuit. The resistance value of the resistive element 45 and the capacitance value of the capacitor 46 are set so that the resonant frequency of the resonant circuit matches or is close to the frequency F of the drive signal D and so that the Q value of the resonant characteristics is an appropriate numerical value.

[0049] In the above configuration, a drive signal D, which is obtained by removing high-frequency components from a drive signal D output from a drive circuit 41_n, is supplied to the drive coil 21_n. The drive signal D is a sinusoidal periodic signal whose voltage fluctuates with a frequency F equal to that of the drive signal D. The voltage amplitude of the drive signal D is, for example, approximately 3.8 Vp-p.

[0050] The voltage detection unit 50 in Fig. 11 detects the detected voltage V_m for each supply period T_n for each of the five strings 15_1 to 15_5. As described above, the detected voltage V_m fluctuates periodically, similar to the drive signal D. If the initial voltage amplitude of the drive signal D0 is 5 Vp-p, the voltage amplitude of the detected voltage V_m will be, for example, approximately 10 mVp-p. The voltage detection unit 50 amplifies the detected voltage V_m to a detectable voltage.

[0051] Fig. 14 is a circuit diagram illustrating the configuration of the voltage detection unit 50. Fig. 14 shows a first end E1 and a second end E2 of each string 15_m. The first end E1 is the end of the string 15_m that is fixed to the head 13, and the second end E2 is the end of the string 15_m that is fixed to the body 10 (bridge 17).

[0052] 14 shows the first end Ea1 and the second end Ea2 of the feedback line 22 and the first end Eb1 and the second end Eb2 of the reference line 23. The first end Eb1 is the end of the reference line 23 located in the positive direction of the Y-axis, and the second end Eb2 is the end of the reference line 23 located in the negative direction of the Y-axis. As described above, the first end E1 of each of the five strings 15_1 to 15_5 is connected to the first end Ea1 of the feedback line 22. Similarly, the first end Eb1 of the reference line 23 is also connected to the first end Ea1 of the feedback line 22.

[0053] A resistive element 51_m is connected in series between the first end E1 of each string 15_m and the feedback line 22. Specifically, one end of the resistive element 51_m is connected to the first end E1 of the string 15_m, and the other end of the resistive element 51_m is connected to the first end Ea1 of the feedback line 22. The resistive element 51_m is a resistor for ensuring the impedance of the detection coil 28_m when the first fret 14_1 is pressed. The resistance value of the resistive element 51_m exceeds the resistance value of the string 15_m. The resistive element 51_m1 is an example of a "first resistive element," and the resistive element 51_m2 is an example of a "second resistive element."

[0054] The resistance component of the strings 15_m themselves differs for each string 15_m due to individual differences. According to the first embodiment, a resistive element 51_m is connected to each string 15_m, thereby reducing the impedance discrepancy between the five strings 15_1 to 15_5. In other words, the impedances of the five strings 15_1 to 15_5 can be equalized. Note that no resistive element 51_m is installed on the reference line 23.

[0055] The voltage detection section 50 includes five detection units 52_1 to 52_5, an output circuit 53, and a reference unit 54. The five detection units 52_1 to 52_5 correspond to different strings 15_m. The second end E2 of each string 15_m is connected to the detection unit 52_m. Each detection unit 52_m is a circuit that detects the detected voltage V_m of the string 15_m. The five detection units 52_1 to 52_5 detect five systems of detected voltages V_1 to V_5 corresponding to the different strings 15_m in parallel. Note that one detection unit 52_m may detect the detected voltages V_m for each of the five strings 15_1 to 15_5 in a time-division manner.

[0056] Each detection unit 52_m includes a band-pass filter 521, an amplifier 522, and a comparator 523. The band-pass filter 521 is composed of two resistors and two capacitors, and selectively passes components of the voltage at the second end E2 of the string 15_m in a frequency band that includes the frequency F0 of the drive signal D. The voltage Va_m processed by the band-pass filter 521 is supplied to the positive input terminal (+) of the amplifier 522.

[0057] The output circuit 53 includes a band-pass filter 531 and a resistor element 532. The band-pass filter 531 selectively passes components of the voltage at the second end Ea2 of the feedback line 22 in a frequency band including the frequency F0 of the drive signal D. The voltage V0 processed by the band-pass filter 531 is supplied to the negative input terminal (-) of the amplifier 522 in each detection unit 52_m. The negative input terminal of the amplifier 522 in each of the five detection units 52_1 to 52_5 is grounded via the resistor element 532. The difference (differential input voltage) between the voltage Va_m and the voltage V0 corresponds to the detection voltage V_m.

[0058] The amplifier 522 of each detection unit 52_m is an amplifier that detects and amplifies the detection voltage V_m of the string 15_m. Specifically, the amplifier 522 amplifies the detection voltage V_m with a gain of, for example, about 45 dB. The amplifier 522 generates a detection voltage U_m by detecting the amplified detection voltage V_m. Specifically, the amplifier 522 outputs a detection voltage U_m having a voltage value corresponding to the voltage amplitude of the detection voltage V_m.

[0059] As described above, the voltage amplitude of the detected voltage V_m changes depending on the position where the string 15_m is pressed, and therefore the voltage value of the detected voltage U_m also changes depending on the position where the string 15_m is pressed. Therefore, it is possible to identify the position where the string 15_m is pressed using the detected voltage U_m. For example, the position where the string is pressed can be identified by determining whether the detected voltage U_m exceeds a predetermined threshold for each supply period T_n.

[0060] Note that, when focusing on any two detection units 52_m1 and 52_m2, the amplifier 522 of the detection unit 52_m1 is an example of a “first detection circuit,” and the amplifier 522 of the detection unit 52_m2 is an example of a “second detection circuit.” Furthermore, the detection voltages V_m1 and U_m1 are an example of a “first detection voltage,” and the detection voltages V_m2 and U_m2 are an example of a “second detection voltage.”

[0061] Incidentally, as a performance style by a performer, in addition to performance in which only one string 15_m of the five strings 15_1 to 15_5 is pressed, performance in which multiple strings 15_m are pressed in parallel is also assumed. When multiple strings 15_m are pressed in parallel, the multiple strings 15_m are electrically connected via fret 14_n. Therefore, when multiple strings 15_m are pressed in parallel, the detected voltage U_m corresponding to each string 15_m is lower than when only one string 15_m is pressed.

[0062] FIG. 15 is an explanatory diagram of the decrease in detected voltage U_1 due to the pressing of multiple strings 15_m. In FIG. 15, the detected voltage U_1 of string 15_1 is plotted on the vertical axis. In FIG. 15, voltage U_1-off represents the detected voltage U_1 when string 15_1 is not pressed (open state), and voltage U_1-on represents the detected voltage U_1 when string 15_1 is pressed. The pressed strings in FIG. 15 are in a state where the performer presses the strings, causing two frets, the 15th fret 14_15 and the 16th fret 14_16, to come into contact with string 15_m. Note that because the spacing between frets 14_n is narrow in the region of fingerboard 12 near the second end E2 of each string 15_m, even when the performer presses one point on string 15_m, two frets 14_n simultaneously come into contact with string 15_m. Taking the above into consideration, in FIG. 15, it is assumed that two frets 14_n (14_15, 14_16) are in contact with the string 15_m.

[0063] FIG. 15 shows the detected voltage U_1-off and the detected voltage U_1-on for each of a number of states in which the number of strings 15_m pressed in parallel by the performer (hereinafter referred to as the "number of simultaneously pressed strings") is different. State 1 is a state in which the four strings 15_2 to 15_5 other than string 15_1 are released. State 2 is a state in which string 15_2 is pressed and strings 15_3 to 15_5 are released. State 3 is a state in which strings 15_2 and 15_3 are pressed and strings 15_4 and 15_5 are released. State 4 is a state in which strings 15_2 to 15_4 are pressed and string 15_5 is released. State 5 is a state in which the four strings 15_2 to 15_5 other than string 15_1 are pressed. As can be seen from FIG. 15, there is a tendency for the detected voltage U_1-off and the detected voltage U_1-on to decrease as the number of simultaneously pressed strings increases.

[0064] In order to accurately identify the pressed position of each string 15_m even when the detected voltage U_m depends on the number of simultaneously pressed strings as described above, in the first embodiment, the voltage of the reference line 23 (hereinafter referred to as "reference voltage R") is used.

[0065] As described above, the reference wire 23 is connected to the feedback wire 22, and thus, like each string 15_m, the reference wire 23 and the feedback wire 22 form a one-turn coil (hereinafter referred to as the "reference coil"). The magnetic flux generated in each drive coil 21_n by the supply of the drive signal D interlinks with the reference coil including the reference wire 23 and the feedback wire 22. Therefore, when a current flows in the drive coil 21_n (primary coil) by the supply of the drive signal D, an electromotive force is generated not only in each detection coil 28_m but also in the reference coil (secondary coil) due to mutual induction caused by the magnetic field generated in the drive coil 21_n. The reference voltage R is the voltage between the feedback wire 22 and the reference wire 23.

[0066] The reference unit 54 in FIG. 14 is a circuit for detecting the reference voltage R. The reference unit 54 includes a band-pass filter 541 and an amplifier 542. Similar to the band-pass filter 521, the band-pass filter 541 selectively passes components of the voltage at the second end Eb2 of the reference line 23 in a frequency band that includes the frequency F0 of the drive signal D. The voltage Vr processed by the band-pass filter 541 is supplied to the positive input terminal (+) of the amplifier 542. The voltage V0 processed by the band-pass filter 541 is supplied to the negative input terminal (-) of the amplifier 542.

[0067] The amplifier 542 is an amplifier that detects and amplifies the voltage Vr of the reference line 23. The configuration of the amplifier 542 is similar to that of the amplifier 522. Therefore, the amplifier 542 amplifies the differential voltage between the voltage Vr of the reference line 23 and the voltage V0 of the feedback line 22, and outputs the reference voltage R by detecting the amplified voltage. In other words, the reference voltage R having a voltage value corresponding to the voltage amplitude of the differential voltage between the voltage Vr and the voltage V0 is output. The amplifier 542 amplifies the differential voltage with a gain of, for example, about 40 dB. In other words, the gain of the amplifier 542 is lower than the gain of the amplifier 522.

[0068] The comparator 523 of each detection unit 52 is a comparator that compares the detection voltage U_m with the reference voltage R and generates an output signal Z_m according to the comparison result. The output signal Z_m is a binary signal that is set to either a high level or a low level for each supply period T_n in synchronization with the supply of the drive signal D to each drive coil 21_n. Specifically, the comparator 523 sets the output signal Z_m to a high level when the detection voltage U_m exceeds the reference voltage R, and sets the output signal Z_m to a low level when the detection voltage U_m is below the reference voltage R. That is, the output signal Z_m is set to a high level when the differential voltage (U_m-R) between the detection voltage U_m and the reference voltage R is positive, and the output signal Z_m is set to a low level when the differential voltage (U_m-R) is negative. As described above, the reference voltage R corresponds to a threshold value that is compared with the detection voltage U_m.

[0069] Fig. 16 is an explanatory diagram of the reference voltage R. Fig. 16 is a graph in which the reference voltages R (R-off, R-on) are plotted alongside Fig. 15, which illustrates the detected voltage U_m. The reference voltage R-off in Fig. 16 is the reference voltage R when the string 15_1 is released, and the reference voltage R-on is the reference voltage R when the string 15_1 is pressed.

[0070] As can be seen from FIG. 16 , the reference voltage R of the reference line 23 fluctuates depending on whether or not the string 15_1 is pressed. Specifically, the reference voltage R-off when the string 15_1 is released exceeds the reference voltage R-on when the string 15_1 is pressed. Furthermore, as can be seen from FIG. 16 , the reference voltages R-off and R-on tend to decrease as the number of simultaneously pressed strings increases. In other words, the detected voltage U_1 and the reference voltage R interact with each other depending on the number of simultaneously pressed strings. Therefore, by analyzing the detected voltage U_m using the reference voltage R as a reference value, it is possible to determine with high accuracy whether or not the string 15_m is pressed (and even the pressed position).

[0071] 17 is a graph showing the differential voltage (U_1-R) between the detected voltage U_1 and the reference voltage R for each of states 1 to 5. As mentioned above, FIG. 17 confirms that the configuration that distinguishes the sign of the differential voltage (U_1-R) between the detected voltage U_m and the reference voltage R makes it possible to determine with high accuracy whether the string 15_1 is pressed. That is, the comparator 523 sets the output signal Z_m to a high level when the differential voltage (U_m-R) between the detected voltage U_m and the reference voltage R is positive, and sets the output signal Z_m to a low level when the differential voltage (U_m-R) is negative.

[0072] As described above, the reference voltage R fluctuates along with each detected voltage U_m depending on the number of simultaneously pressed strings. Therefore, according to the above-described embodiment in which each detected voltage U_m is compared with the reference voltage R, the pressed position of each string 15_m can be determined with high accuracy even when multiple strings 15_m are pressed simultaneously.

[0073] FIG. 18 is an explanatory diagram of the transient response of the amplifier 522. FIG. 18 shows the waveform of the drive signal D along with the time variations of the detected voltage V_m and the detected voltage U_m. It can be seen from FIG. 18 that it takes a time length equivalent to approximately 10 waves of the drive signal D to reach a steady voltage. Assuming the frequency F of the drive signal D is 2.3 MHz, the time length required for the detected voltage U_m to rise is approximately 4 microseconds. Meanwhile, from the point at which the supply of the drive signal D to the drive coil 21_n is terminated, the detected voltage U_m falls over a time length equivalent to approximately 26 waves of the drive signal D (approximately 11 microseconds).

[0074] As described above, the time required for the detection voltage U_m to fall is longer than the time required for the detection voltage U_m to rise. In other words, the rise of the detection voltage U_m is faster than the fall. Therefore, the time length of each supply period T_n is ensured to be the time length required for the detection voltage U_m to fall. Assuming that the number N of frets 14_n is 24, the time required to supply the drive signal D to all frets 14_n is approximately 0.27 microseconds (= 24 × 26 × 1 / 2.3 MHz). Therefore, it is possible to identify the fingering position of each string 15_m with a delay sufficiently short that it is imperceptible to the player.

[0075] The string pressing analysis unit 60A identifies the pressed position of each string 15_m based on the output signal Z_m corresponding to that string 15_m. For example, when the output signal Z_m changes from low to high during the supply period T_n, the string pressing analysis unit 60A identifies the fret 14_n-1 as the pressed position of the string 15_m.

[0076] B: Third Embodiment A third embodiment will now be described. Note that, in the following exemplary embodiments, elements that have the same functions as those in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and detailed descriptions of each element will be omitted as appropriate.

[0077] 19 is an explanatory diagram of the principle of detecting the fingering position of any one string 15_m in the third embodiment. Similar to the first embodiment, the electric bass guitar 100 of the third embodiment is equipped with N drive coils 21_1 to 21_N corresponding to different frets 14_n. A drive signal D is sequentially supplied to each of the N drive coils 21_1 to 21_N in a time-division manner.

[0078] In the first embodiment, the drive coil 21_n is installed between adjacent frets 14_n and 14_n-1 (FIG. 2). That is, the drive coil 21_n is located in the positive direction of the Y axis relative to the fret 14_n. In the third embodiment, the drive coil 21_n is installed between adjacent frets 14_n and 14_n+1, as shown in FIG. 19. That is, the drive coil 21_n is located in the negative direction of the Y axis relative to the fret 14_n.

[0079] Similar to the first embodiment, the feedback line 22 is a wiring that extends in the Y-axis direction with a gap between it and each string 15_m, and includes a first end Ea1 and a second end Ea2. In the first embodiment, the first end E1 of each string 15_m is connected to the feedback line 22. In the third embodiment, each string 15_m is not electrically connected to the feedback line 22. Each of the N frets 14_1 to 14_N is electrically connected to the feedback line 22, similar to the first embodiment. Note that in the third embodiment, the reference line 23 described above may be omitted.

[0080] 20 and 21 show the drive coils 21_n-1 and 21_n, and the frets 14_n-1 and 14_n. The voltage C0_m,n in Fig. 20 and 21 is the voltage of the string 15_m during the period when the drive signal D is supplied to any one of the drive coils 21_n.

[0081] In Figure 20, it is assumed that string 15_m is not pressed. In the state shown in Figure 20, the feedback line 22 and string 15_m are electrically insulated, so detection coil 28_m is not formed. Therefore, even if a current flows through drive coil 21_n-1 due to the supply of drive signal D during supply period T_n-1, voltage C0_m,n-1 of string 15_m does not substantially fluctuate. Similarly, even if a current flows through drive coil 21_n due to the supply of drive signal D during the immediately following supply period T_n, voltage C0_m,n of string 15_m does not substantially fluctuate.

[0082] 21, it is assumed that the performer has pressed down on the string 15_m, causing it to come into contact with the fret 14_n. In other words, the fret 14_n is the position where the string is pressed. As a result of the string 15_m coming into contact with the fret 14_n, the string 15_m, the fret 14_n, and the feedback wire 22 form a one-turn detection coil 28_m.

[0083] 21 , even if a current flows through drive coil 21_n-1 due to the supply of drive signal D during supply period T_n-1, voltage C0_m,n-1 of string 15_m does not substantially fluctuate. On the other hand, when a current flows through drive coil 21_n due to the supply of drive signal D during the immediately following supply period T_n, mutual induction caused by the magnetic field generated in drive coil 21_n generates an electromotive force in detection coil 28_m (secondary coil) formed by string 15_m, fret 14_n, and feedback line 22. Therefore, voltage C0_m,n fluctuates periodically, just like drive signal D.

[0084] As shown in the above example, when the string 15_m and the fret 14_n are not in contact ( FIG. 20 ), the voltages C0_m,n-1 and C0_m,n of the string 15_m are substantially the same, whereas when the string 15_m and the fret 14_n are in contact due to the string being pressed ( FIG. 21 ), the voltages C0_m,n-1 and C0_m,n are different. That is, the voltages C0_m,1 to C0_m,n-1 are different from the voltages C0_m,n to C0_m,N. Therefore, it is possible to identify the pressed position of each string 15_m based on whether or not there is a change in the N voltages C0_m,1 to C0_m,N detected during different supply periods T_n. Specifically, as in the example above, if the voltages C0_m,1 to C0_m,n-1 differ from the voltages C0_m,n to C0_m,N, it can be determined that the fret 14_n on the string 15_m is pressed.

[0085] 22 is a block diagram illustrating the configuration of a detection device 30 according to the third embodiment. The detection device 30 of the third embodiment includes a signal supply unit 40, a signal output unit 55, and a string pressing analysis unit 60B. As in the first embodiment, the signal supply unit 40 supplies a drive signal D to each of the N drive coils 21_1 to 21_N. Specifically, the drive signal D is supplied to each of the N drive coils 21_1 to 21_N in a time-division manner for each supply period T_n.

[0086] 23 is a block diagram illustrating the configuration of the signal output unit 55 and the string pressing analysis unit 60B. The signal output unit 55 generates a voltage C_m,n corresponding to the voltage C0_m,n of each string 15_m, and a voltage Cref_n (hereinafter referred to as the "reference voltage") corresponding to the voltage Cref0_n of the feedback line 22. As described above with reference to FIGS. 20 and 21, the voltage C0_m,n is the voltage of the string 15_m during the supply period T_n when the drive signal D is supplied to the drive coil 21_n. On the other hand, the voltage Cref0_n is the voltage of the feedback line 22 during the supply period T_n.

[0087] The signal output unit 55 includes five output circuits 56_1 to 56_5 corresponding to different strings 15_m and an output circuit 57 corresponding to the feedback line 22. The output circuit 56_m generates a voltage C_m,n corresponding to the voltage C0_m,n of the string 15_m during the supply period T_n. Specifically, the output circuit 56_m includes an amplifier that amplifies the voltage C0_m,n, a rectifier circuit that rectifies the amplified voltage C0_m,n, and a smoothing circuit that smooths the rectified voltage C_m,n. Therefore, the voltage C_m,n is a DC voltage corresponding to the amplitude of the voltage C0_m,n. Similarly, the output circuit 57 generates a reference voltage Cref_n corresponding to the voltage Cref0_n of the feedback line 22 during the supply period T_n. Specifically, the output circuit 57 includes an amplifier that amplifies the voltage Cref0_n, a rectifier circuit that rectifies the amplified voltage Cref0_n, and a smoothing circuit that smoothes the rectified voltage Cref0_n. Therefore, the reference voltage Cref_n is a DC voltage that corresponds to the amplitude of the voltage Cref0_n.

[0088] The string pressing analysis unit 60B determines whether or not each string 15_m is pressed and the position (pressed position) of the string 15_m based on the voltage C_m,n of each string 15_m and the reference voltage Cref_n of the feedback line 22. Specifically, the string pressing analysis unit 60B includes a control device 61, a storage device 62, five A / D converters 63_1 to 63_5 corresponding to different strings 15_m, and an A / D converter 64 corresponding to the feedback line 22.

[0089] The A / D converter 63_m converts the voltage C_m,n supplied from the output circuit 56_m from analog to digital. The A / D converter 64 converts the reference voltage Cref_n supplied from the output circuit 57 from analog to digital.

[0090] The control device 61 is a single or multiple processors that execute various types of arithmetic processing and control processing. Specifically, the control device 61 is configured by one or more types of processors, such as a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0091] The storage device 62 is one or more memories that store programs executed by the control device 61 and various data used by the control device 61. For example, a recording medium such as a semiconductor recording medium or a magnetic recording medium, or a combination of multiple types of recording media, is used as the storage device 62.

[0092] The detection data is stored for each unit period in the storage device 62. The unit period is a period corresponding to a cycle in which the drive signal D is supplied to each of the N drive coils 21_1 to 21_N. In other words, the unit period is a period corresponding to N periods in which the drive signal D is supplied to each drive coil 21_n.

[0093] 24 is a schematic diagram of the detection data. The detection data includes N voltages C_m,1 to C_m,N corresponding to different supply periods T_n for each of the five strings 15_1 to 15_5. Each voltage C_m,n is a numerical value converted by the A / D converter 63_m. The voltage C_m,n can also be expressed as a numerical value corresponding to the drive coil 21_n or a numerical value corresponding to the fret 14_n. The detection data also includes N reference voltages Cref_1 to Cref_N corresponding to different supply periods T_n. Each reference voltage Cref_n is a numerical value converted by the A / D converter 64.

[0094] 25 is a schematic diagram showing the temporal changes in the N voltages C_m,1 to C_m,N stored in the detection data for any one string 15_m, and the N reference voltages Cref_1 to Cref_N stored in the detection data for the feedback line 22. In FIG. 25, the total number N of frets 14_n is assumed to be 24, and one fret 14_18 is assumed to be pressed. Of the N frets 14_1 to 14_N, the final fret 14_N (N=24), which is closest to the bridge 17, will be referred to as the "last fret" in the following explanation.

[0095] 25, the voltages C_m,1 to C_m,17 from the first supply period T_1 in the unit period to the supply period T_17 immediately preceding the supply period T_18 corresponding to the pressed position are lower than the voltages C_m,18 to C_m,24 from the supply period T_18 corresponding to the pressed position to the supply period T_24 corresponding to the last fret 14 24. Similarly, the reference voltages Cref_1 to Cref_17 from the first supply period T_1 to supply period T_17 in the unit period are lower than the reference voltages Cref_18 to Cref_24 from the supply period T_18 corresponding to the pressed position to supply period T_24.

[0096] 25 shows the difference (hereinafter referred to as the "detected voltage") V_m,n between the voltage C_m,n and the reference voltage Cref_n during each supply period T_n (V_m,n = |C_m,n - Cref_n|). As can be seen from FIG. 25, the detected voltages V_m,1 to V_m,17 from the first supply period T_1 within the unit period to the supply period T_17 immediately preceding the supply period T_18 corresponding to the pressed position are lower than the detected voltages V_m,18 to V_m,24 from the supply period T_18 corresponding to the pressed position to the supply period T_24 corresponding to the last fret 14_24. As can be seen from the above explanation, the presence or absence and position of the pressed string on string 15_m (the pressed position) can be determined depending on whether or not the detected voltage V_m,n changes within the unit period and the point in time.

[0097] 26 and 27 are flowcharts of the process (hereinafter referred to as the "string pressing analysis process") that the control device 61 (string pressing analysis unit 60B) executes to identify the string pressing position of each string 15_m. The string pressing analysis process is executed each time the detection data is updated in each unit period. In other words, the string pressing analysis process is executed for each unit period.

[0098] When the string pressing analysis process begins, the control device 61 selects the maximum value Cmax from five voltages C_1,N to C_5,N corresponding to different strings 15_m (S1). The voltage C_m,N that is a candidate for selection as the maximum value Cmax is the voltage that corresponds to the final fret 14_N among the N voltages C_m,1 to C_m,N corresponding to the string 15_m. In other words, the maximum value Cmax is selected from the five voltages C_1,N to C_5,N during the supply period T_N in which the drive signal D is supplied to the final-stage drive coil 21_N.

[0099] The control device 61 selects one of the five strings 15_1 to 15_5 (hereinafter referred to as the "selected string 15_m") (S2). For example, the control device 61 initializes the number m of the selected string 15_m to "1." The control device 61 determines whether or not processing has been performed for all five strings 15_1 to 15_5 (S3). If processing has been performed for all strings 15_m (S3: YES), the control device 61 ends the string pressing analysis processing.

[0100] If there is an unselected string 15_m (S3: NO), the control device 61 calculates the differential voltage δ_m for the selected string 15_m (S4). The differential voltage δ_m is the value obtained by subtracting the voltage C_m,N corresponding to the selected string 15_m and the last fret 14_N from the maximum value Cmax (δ_m = Cmax - C_m,N).

[0101] The voltage C_m,n of the selected string 15_m may be affected by the other strings 15_m'. The voltage C_m,n of the selected string 15_m may increase due to the influence of the other strings 15_m',n even when the selected string 15_m is not actually pressed. That is, when the voltage C_m,n of the selected string 15_m is affected by the other strings 15_m' (hereinafter referred to as a "crosstalk state"), the differential voltage δ_m increases compared to when the voltage C_m,n of the selected string 15_m is not affected by the other strings 15_m'. Taking these trends into consideration, the control device 61 determines whether the selected string 15_m is in a crosstalk state based on whether the differential voltage δ_m exceeds a predetermined threshold value Vth1 (S5).

[0102] Specifically, if the differential voltage δ_m exceeds the threshold Vth1 (S5: YES), the control device 61 determines that the selected string 15_m is in a crosstalk state and proceeds to step S16. On the other hand, if the differential voltage δ_m is below the threshold Vth1 (S5: NO), the control device 61 determines that the selected string 15_m is not in a crosstalk state and proceeds to step S6. Note that if the differential voltage δ_m is equal to the threshold Vth1, the control device 61 may make either a positive or negative determination.

[0103] The control device 61 selects the maximum value Cmax_m from the N voltages C_m,1 to C_m,N corresponding to the selected string 15_m (S6). As mentioned above, the voltage C_m,n increases when a string is pressed, so when the selected string 15_m is in an open state (not pressed), the maximum value Cmax_m is maintained at a low voltage. Taking these trends into consideration, the control device 61 determines whether the selected string 15_m is in an open state based on whether the maximum value Cmax_m of the selected string 15_m is below a predetermined threshold value Vth2 (S7).

[0104] Specifically, if the maximum value Cmax_m is below the threshold value Vth2 (S7: YES), the control device 61 determines that the selected string 15_m is in the open state, and proceeds to step S16. On the other hand, if the maximum value Cmax_m is above the threshold value Vth2 (S7: NO), the control device 61 determines that the selected string 15_m is not in the open state, and proceeds to step S8 in Fig. 27. Note that if the maximum value Cmax_m is equal to the threshold value Vth2, the control device 61 may make either a positive or negative determination.

[0105] The control device 61 selects one of the N frets 14_1 to 14_N (hereinafter referred to as the "selected fret 14_n") (S8). For example, the control device 61 initializes the number n of the selected fret 14_n to "1." Each of the N frets 14_1 to 14_N is selected as the selected fret 14_n in order in the negative direction of the Y axis. The control device 61 determines whether or not the process has been performed for all of the N frets 14_1 to 14_N (S9).

[0106] If there is an unselected fret 14_n (S9: NO), the control device 61 calculates the detected voltage V_m,n corresponding to the selected string 15_m and the selected fret 14_n (S10). As described above, the detected voltage V_m,n is the difference between the voltage C_m,n during each supply period T_n and the reference voltage Cref_n (V_m,n = |C_m,n - Cref_n|). As explained above, the control device 61 (string pressing analysis unit 60B) of the third embodiment functions as an element (voltage detection unit) that detects the detected voltage V_m,n between each string 15_m and the feedback line 22.

[0107] 25, there is a tendency for the detected voltage V_m,n to increase when the string corresponding to the selected fret 14_n is pressed. Taking this tendency into consideration, the control device 61 determines whether the detected voltage V_m,n is below a predetermined threshold value Vth3 (S11).

[0108] If the detected voltage V_m,n is below the threshold Vth3 (S11: YES), the control device 61 sets the string-pressed flag F_m,n to a value f0 (e.g., 0) (S12). On the other hand, if the detected voltage V_m,n is above the threshold Vth3 (S11: NO), the control device 61 sets the string-pressed flag F_m,n to a value f1 (e.g., 1) that is different from the value f0 (S13). The string-pressed flag F_m,n is information used to search for the pressed position of the selected string 15_m. The value f0 of the string-pressed flag F_m,n indicates that the selected fret 14_n and the feedback line 22 are not short-circuited. On the other hand, the value f1 of the string-pressed flag F_m,n indicates that the selected fret 14_n and the feedback line 22 are in contact with each other due to the string being pressed.

[0109] The control device 61 adds "1" to the number n of the selected fret 14_n (S14). In other words, the selected fret 14_n is changed. After the setting of the pressed flags F_m,n for all N frets 14_1 to 14_N has been executed, the result of the determination in step S9 transitions from negative to positive. The control device 61 identifies the pressed position of the selected string 15_m using the N pressed flags F_m,1 to F_m,N corresponding to the different frets 14_n (S15). Specifically, the control device 61 identifies the position in the series of N pressed flags F_m,1 to F_m,N corresponding to the boundary between the numerical values ​​f0 and f0 as the pressed position of the selected string 15_m. As described above, the string pressing analysis unit 60B of the third embodiment identifies the fret 14_n that is in contact with the string 15_m among the N frets 14_1 to 14_N as the string pressing position in accordance with the change in the detected voltage V_m,n detected each time the drive signal D is supplied.

[0110] In step S16 of Figure 26, the control device 61 adds "1" to the number m of the selected string 15_m. In other words, the selected string 15_m is changed. After performing the above process for all five strings 15_1 to 15_5, the result of the determination in step S3 changes from negative to positive. As explained above, the presence or absence and position (string-pressing position) of each of the five strings 15_1 to 15_5 are identified.

[0111] The third embodiment achieves the same effects as the first embodiment. Furthermore, in the third embodiment, the control device 61 executes a program to detect the fingering position according to each detected voltage V_m,n. Therefore, compared to the first embodiment, the configuration and operation of the detection device 30 are simplified, which is an advantage.

[0112] C: Fourth Embodiment Figure 28 is a block diagram illustrating the configuration of the signal output unit 55 and the string pressing analysis unit 60B in the fourth embodiment. In the fourth embodiment, a DC voltage B is applied to each of the five strings 15_1 to 15_5. The DC voltage B is a bias voltage maintained at a predetermined voltage value (e.g., 5 V). For example, the signal supply unit 40 applies the DC voltage B to each string 15_m.

[0113] Similar to the first embodiment, the signal output unit 55 of the fourth embodiment includes five output circuits 56_1 to 56_5 corresponding to different strings 15_m, and an output circuit 57 corresponding to the feedback line 22. Similar to the first embodiment, each output circuit 56_m generates a voltage C_m,n corresponding to the voltage C0_m,n of the string 15_m during the supply period T_n. Specifically, the output circuit 56_m includes a DC removal circuit that removes a DC component (DC voltage B) from the voltage C0_m,n, and an electric circuit (e.g., an amplifier, a rectifier circuit, a smoothing circuit) that generates a voltage C_m,n from the voltage after removal.

[0114] Furthermore, the output circuit 56_m of the fourth embodiment includes a comparator 58_m in addition to the above circuits that generate a voltage C_m,n corresponding to the voltage C_m,n. The comparator 58_m compares the voltage C0_m,n of the string 15_m, which includes the DC voltage B, with a predetermined threshold value. The threshold value is a predetermined voltage that is lower than the DC voltage B.

[0115] The comparator 58_m generates a binary signal W_m according to the result of comparing the voltage C0_m,n with a threshold. When the voltage C0_m,n exceeds the threshold, the comparator 58_m outputs a high-level signal W_m. On the other hand, when the voltage C0_m,n is below the threshold, the comparator 58_m outputs a low-level signal W_m.

[0116] When the string 15_m is in the open state, the voltage C0_m,n is a high voltage that is close to the DC voltage B, and therefore the signal W_m is set to a high level. On the other hand, when the string 15_m is pressed and connected to the feedback line 22, the voltage C0_m,n drops to a voltage below the DC voltage B. Therefore, the signal W_m is set to a low level. As explained above, the signal W_m is a binary signal that indicates whether the string 15_m is in the open state or not.

[0117] Each signal W_m is supplied to a string pressing analysis unit 60B (control device 61). The control device 61 determines whether or not the corresponding string 15_n of the five strings 15_1 to 15_5 is in an open state based on the level of the signal W_m. Specifically, the control device 61 determines that the string 15_n is in an open state when the signal W_m is at a high level, and determines that the string 15_n is not in an open state when the signal W_m is at a low level. As described above, the detection device 30 (signal output unit 55 and string pressing analysis unit 60B) of the fourth embodiment functions as an element (string pressing determination unit) that determines whether or not a string 15_m is pressed based on the voltage C0_m,n of each string 15_m.

[0118] As described above, in the fourth embodiment, whether or not the string 15_m is pressed is determined based on the signal W_m. Therefore, the steps of the string pressing analysis process (S6, S7) for determining whether or not the selected string 15_m is in an open state may be omitted.

[0119] The fourth embodiment also achieves the same effects as the first and third embodiments. Furthermore, the fourth embodiment has the advantage that it is possible to accurately determine whether or not a string 15_m is pressed, based on the voltage of the string 15_m to which the DC voltage B is applied.

[0120] D: Fifth Embodiment Figure 29 is a cross-sectional view of the neck 11 and fingerboard 12 according to the fifth embodiment. Figure 29 shows both a cross section perpendicular to the direction in which the neck 11 extends (the direction of the Y axis) and cross sections along that direction (cross sections taken along lines A-A and B-B).

[0121] 29 , the protrusion 141 of each fret 14_n in the fifth embodiment is a flat leg that protrudes from the bottom surface of the portion of the fret 14_n that extends in the X-axis direction toward the neck 11 and fingerboard 12, and extends in the X-axis direction between both ends of the fret 14_n. In other words, the protrusion 141 in the fifth embodiment is continuous across the entire width of the fret 14_n.

[0122] Meanwhile, in addition to the same mounting holes 122 as in the first embodiment, mounting grooves 125 corresponding to each fret 14_n are formed on the surface of the fingerboard 12. The mounting grooves 125 are bottomed grooves that extend in the X-axis direction across the entire width of the fingerboard 12. The mounting holes 122 are formed in the centers of the mounting grooves 125 in the X-axis direction. The gaps between the mounting grooves 125 (the spacing in the Y-axis direction) are smaller than the gaps between the mounting holes 122.

[0123] 29 as a cross section taken along the line B-B, the fret 14_n is fixed to the fingerboard 12 by inserting the protrusion 141 into the mounting groove 125. That is, one side surface of the protrusion 141 contacts one inner wall surface of the mounting groove 125, and the other side surface of the protrusion 141 contacts the other inner wall surface of the mounting groove 125.

[0124] 29 , in the fifth embodiment, the connection portion 24_n in each of the above-described embodiments is replaced with a connection portion 25_n. The connection portion 25_n is a flexible conductor that can be deformed by an external force. For example, a conductive foam formed by covering the surface of a foam made of an elastic material such as polyurethane with a conductive film is used as the connection portion 25_n.

[0125] As in the first embodiment, the fingerboard 12 is formed with mounting holes 122 corresponding to each fret 14_n. The connection portions 25_n are inserted into the mounting holes 122. The lower surfaces of the connection portions 25_n contact the mounting surface 20a of the wiring board 20 and are electrically connected to the feedback wires 22 on the mounting surface 20a. Note that, because the connection portions 25_n are deformable, the planar shape of the mounting holes 122 is arbitrary. For example, in addition to a form in which the mounting holes 122 are formed with a rectangular shape in a plan view, a form in which the mounting holes 122 are formed with an elliptical or oblong shape in a plan view in the fingerboard 12 is also conceivable.

[0126] As shown in the A-A cross section in Figure 29, the central portion of the protrusion 141 of the fret 14_n, which is located inside the mounting hole 122, presses against the top surface of the connection portion 25_n. The pressure from the protrusion 141 causes the connection portion 25_n to locally deform. Specifically, the protrusion 141 bites into the connection portion 25_n. Therefore, the connection portion 25_n is held in a compressed state between the protrusion 141 and the wiring board 20. The bottom surface of the connection portion 25_n may or may not be bonded to the mounting surface 20a, for example, with a conductive bonding material.

[0127] In the fifth embodiment, the fret 14_n and the wiring board 20 (feedback line 22) are electrically connected by flexible connection parts 25_n that are deformed when pressed by the protrusions 141. Therefore, even if there is an error in the position or dimensions of the fret 14_n, the fret 14_n can be reliably connected to the feedback line 22.

[0128] Furthermore, the protrusions 141 for fixing the frets 14_n to the fingerboard 12 also serve to electrically connect the frets 14_n to the feedback wires 22. Therefore, there is an advantage that the frets of conventional stringed instruments, in which the protrusions 141 extend across the entire width of the frets 14_n, can be used in the present disclosure.

[0129] 29 illustrates an example in which wiring board 20 is housed in groove 112 formed in neck 11, but as illustrated in Fig. 30, wiring board 20 may also be housed in groove 123 formed in fingerboard 12. In the configuration of Fig. 30, the surface of neck 11 facing fingerboard 12 is a flat surface in which groove 112 is omitted.

[0130] Furthermore, in a configuration in which the wiring board 20 is housed in the groove 123 of the fingerboard 12, a support member 124 may be further provided to close the opening of the groove 123, as illustrated in FIG. 31 . The support member 124 is a plate-like member (filler) formed into a shape similar to that of the groove 123 in a plan view. The wiring board 20 is positioned between the support member 124 and the bottom surface of the groove 123 of the fingerboard 12. The support member 124 may also be composed of multiple support pieces spaced apart from one another in the longitudinal direction of the groove 123 (the direction of the Y-axis). Each support piece is a member that extends in the direction of the X-axis between the side walls of the groove 123.

[0131] E: Modifications Specific modifications that can be added to the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate within the scope of not mutually contradicting each other.

[0132] (1) In the above-described embodiments, the signal supply unit 40 includes a drive circuit 41_n for each drive coil 21_n. However, the configuration of the signal supply unit 40 is not limited to the above examples. For example, the signal supply unit 40 illustrated in FIG. 32 may be used.

[0133] 32, a plurality (N) of drive coils 21 are divided into K sets (hereinafter referred to as "drive coil groups") G_1 to G_K, each consisting of a predetermined number of coils. Note that the number of drive coils 21 belonging to each drive coil group G_k (k=1 to K) may differ. The signal supply unit 40 includes a drive circuit 41_k and a distribution circuit 48_k for each of the K drive coil groups G_1 to G_K.

[0134] The selection signal S in Fig. 32 is a control signal that sequentially selects each of the K drive coil groups G_1 to G_K in a time-division manner. Each of the K drive coil groups G_1 to G_K is sequentially selected for each selection period by the selection signal S. During the selection period in which the drive coil group G_k is selected, the drive circuit 41_k outputs a drive signal D0. Furthermore, during the selection period in which the drive coil group G_k is selected, the distribution circuit 48_k outputs the drive signal D0 to each of the multiple drive coils 21 belonging to the drive coil group G_k in a time-division manner. According to the configuration in Fig. 32, the number of drive circuits 41_k can be reduced compared to the above-mentioned embodiments.

[0135] (2) In the above-described embodiments, the magnetic flux of each drive coil 21_n is linked to the detection coil 28_m corresponding to each of the five strings 15_1 to 15_5. In the above-described embodiments, each drive coil 21_n is shared by the five strings 15_1 to 15_5. However, the drive coil 21_n may be formed individually for each of the five strings 15_1 to 15_5.

[0136] (3) In the above-described embodiments, the voltage detection unit 50 compares each detected voltage U_m with the reference voltage R, but the function of the voltage detection unit 50 is not limited to the above examples. For example, the function of comparing each detected voltage U_m with the reference voltage R or the function of generating a detected voltage U_m corresponding to the detected voltage V_m may be omitted from the voltage detection unit 50. As can be understood from the above examples, the voltage detection unit 50 is simply expressed as an element that detects the detected voltage V_m.

[0137] (4) The shapes and positions of the feedback line 22 and the reference line 23 are not limited to the examples described above. For example, the feedback line 22 may be installed on the mounting surface 20 a of the wiring board 20, and the reference line 23 may be installed on the surface opposite the mounting surface 20 a. Alternatively, the feedback line 22 and the reference line 23 may be installed on separate wiring boards. The feedback line 22 and the reference line 23 are not limited to conductive patterns and may be formed, for example, by linear conductors.

[0138] (5) In the above-described embodiments, the reference voltage R compared with the detected voltage U_m varies depending on the number of simultaneously pressed strings. However, the reference voltage R may be a fixed voltage. For example, as can be seen from FIG. 16 , by setting the reference voltage R to a fixed voltage of approximately 0.6 to 0.7 V, it is possible to detect the pressed position of each string 15_m even when multiple strings 15_m are pressed in parallel. However, from the perspective of detecting the pressed position of each string 15_m with high accuracy when multiple strings 15_m are pressed in parallel, the above-described embodiments in which the reference voltage R varies depending on the number of simultaneously pressed strings are preferable.

[0139] (6) The output signals Z_m generated by the voltage detection unit 50 may be used for any purpose. For example, performance data specifying the string-pressing positions of a performer in chronological order may be generated and stored by analyzing the output signals Z_m. Furthermore, musical tones corresponding to the string-pressing positions may be reproduced.

[0140] (7) In the above-described embodiments, the drive signal D is sequentially supplied to each fret 14_n from the first fret 14_1 to the Nth fret 14_N. However, the order in which the drive signal D is supplied to each fret 14_n is not limited to the above examples. For example, the drive signal D may be sequentially supplied to each fret 14_n from the Nth fret 14_N to the first fret 14_1. Furthermore, for example, the operation of sequentially supplying the drive signal D to each odd-numbered fret 14_n and the operation of sequentially supplying the drive signal D to each even-numbered fret 14_n may be alternately repeated.

[0141] (8) In the first embodiment, the protrusion 141 protrudes from the center of the fret 14_n ( FIG. 8 ). As illustrated in FIG. 33 , even in the first embodiment in which the connection 24_n (connection terminal or metal fitting) is used to connect the feedback line 22 to the fret 14_n, the protrusion 141 may extend in the X-axis direction across the entire width of the fret 14_n, as in the fourth embodiment. Also, as illustrated in FIG. 33 , the configuration of FIG. 30 in which the wiring board 20 is housed in the groove 123 of the fingerboard 12 and the configuration of FIG. 31 in which the opening of the groove 123 is closed by the support member 124 are similarly applicable to the first embodiment.

[0142] (9) In the above embodiments, the electric bass guitar 100 is used as an example of a stringed instrument, but the present disclosure can be applied to any type of stringed instrument. For example, the present disclosure can be applied to electric stringed instruments such as electric guitars in addition to the electric bass guitar 100. Furthermore, the stringed instruments to which the present disclosure can be applied are not limited to electric stringed instruments that electrically or magnetically detect the vibration of each string. For example, the present disclosure can also be applied to natural stringed instruments that produce sound through resonance within the internal space of the instrument body. In other words, the present disclosure can be applied to detect and record string pressings by a player in parallel with the normal performance of a natural stringed instrument. As described above, the present disclosure can be applied to any type of stringed instrument that has frets 14_n that come into contact with strings 15_m when pressed by the player.

[0143] (10) In the above-described embodiments, for convenience, an embodiment in which the number of strings 15_m is five is illustrated, but the number of strings 15_m can be changed as desired depending on, for example, the type of stringed instrument. The present disclosure is also applicable to stringed instruments such as mandolins in which multiple pairs of strings 15_m are provided, with each pair consisting of two strings 15_m played in parallel with each other.

[0144] F: Supplementary Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0145] A stringed instrument according to one aspect (aspect 1) of the present disclosure comprises a neck, a plurality of conductive frets arranged at intervals along the neck, a plurality of conductive strings capable of contacting any of the plurality of frets, a plurality of drive coils respectively corresponding to the plurality of frets, a signal supply unit that supplies a drive signal to each of the plurality of drive coils, a feedback line connected to each of the plurality of frets, and a voltage detection unit that detects a first detected voltage between a first string of the plurality of strings and the feedback line during a period in which the drive signal is supplied to each of the plurality of drive coils.

[0146] In the above configuration, when a drive signal is supplied to each drive coil, a current flows through the drive coils, generating an electromotive force in the detection coil, which includes the first string and the feedback wire, due to mutual induction using the magnetic field generated in the drive coils. Therefore, by detecting the first detection voltage between the first string and the feedback wire, it is possible to identify the fret among the multiple frets that is in contact with the first string (i.e., the string-pressing position). This configuration reduces the current flowing through the strings compared to configurations in which an electromotive force is generated in the drive coils on the fingerboard due to mutual induction caused by the supply of a drive signal to the strings. Therefore, the string-pressing position can be detected quickly and accurately while minimizing the effect on the detection (pickup) of vibrations generated in the strings by playing.

[0147] The "drive signal" is a signal that causes the drive coil to generate a magnetic field. The drive signal is, for example, a periodic signal whose voltage fluctuates periodically. The drive signal is supplied sequentially to each of the multiple drive coils.

[0148] The term "first string" refers to any one string selected from the multiple strings of a stringed instrument, and is not limited to the lowest string. A stringed instrument may have any number of strings. Furthermore, a "stringed instrument" is, for example, an electric stringed instrument such as an electric guitar or electric bass. However, the term "stringed instrument" is not limited to electric stringed instruments that detect string vibrations electrically or magnetically. In other words, the present invention also applies to natural stringed instruments that produce sound through resonance within the internal space of the instrument body.

[0149] In a specific example (Aspect 2) of Aspect 1, the feedback wire is connected to a portion of the first string that is located closer to the tip of the neck than the plurality of frets, and the first detection voltage is a voltage between the feedback wire and a portion of the first string that is located closer to the base of the neck than the plurality of frets. This aspect makes it possible to detect contact of the first string with any of a plurality of frets throughout the neck.

[0150] In a specific example (Aspect 3) of Aspect 1 or Aspect 2, the plurality of strings includes a second string, the first string and the second string are connected to the feedback line, and the voltage detection unit includes a first detection circuit that detects the first detected voltage and a second detection circuit that detects a second detected voltage between the second string and the feedback line. According to the above aspect, the first string and the second string are connected to the feedback line. Therefore, compared to an embodiment in which the first string and the second string are each connected to separate feedback lines, the configuration of the stringed instrument can be simplified by reducing the number of feedback lines.

[0151] In a specific example (Aspect 4) of Aspect 3, the magnetic field generated in each of the plurality of drive coils interlinks with a detection coil including the first string and the feedback line and a detection coil including the second string and the feedback line. In the above aspect, a drive coil is shared by both the detection coil including the first string and the feedback line and the detection coil including the second string and the feedback line. Therefore, compared to an arrangement in which a drive coil is individually installed for each string, the number of drive coils can be reduced, simplifying the configuration of the stringed instrument. Moreover, because the first string and the second string are connected to the feedback line, the size of the drive coil can be reduced compared to an arrangement in which the first string and the second string are connected to different feedback lines.

[0152] A specific example (Aspect 5) of Aspect 3 or Aspect 4 further includes a first resistive element connected between the feedback line and a portion of the first string that is closer to the tip of the neck than the frets, and a second resistive element connected between the feedback line and a portion of the second string that is closer to the tip of the neck than the frets. According to the above aspect, resistive elements are connected between the feedback line and each of the first and second strings, ensuring the impedance of the detection coil and reducing the impedance difference between the first and second strings.

[0153] A specific example (Aspect 6) of any one of Aspects 1 to 5 further includes a fingerboard mounted on the neck, the frets being mounted on the fingerboard, the fingerboard being positioned between the first string and the feedback line, and the drive coils being positioned between the fingerboard and the feedback line. In the above aspect, the drive coils are mounted between the fingerboard and the feedback line. That is, the drive coils are not exposed to the outside. Therefore, the drive coils can be mounted while maintaining the appearance of the fingerboard.

[0154] A specific example of Aspect 6 (Aspect 7) includes a wiring board installed between the neck and the fingerboard and a plurality of connection parts installed on the surface of the wiring board, the plurality of drive coils and the feedback line installed on the wiring board, each of the plurality of frets including a protrusion inserted into the fingerboard, each of the plurality of connection parts connected to the protrusion of the fret corresponding to the connection part. According to the above aspect, the protrusion inserted into the fingerboard on each fret is connected to the connection part of the wiring board. Therefore, each fret can be electrically connected to the feedback line using a simple configuration that does not require wiring.

[0155] In a specific example (Aspect 8) of Aspect 7, each of the plurality of connection portions is a flexible conductor that is deformed by being pressed by the protrusion. According to this aspect, the plurality of frets and the feedback line are electrically connected by the conductor compressed by the pressure from the protrusion. Therefore, even if there is an error in the position or size of each fret, it is possible to reliably establish electrical continuity between the fret and the feedback line.

[0156] In a specific example (Aspect 9) of any of Aspects 1 to 8, the instrument further includes a reference wire that does not contact the plurality of frets, the reference wire extending along the neck and connected to the feedback wire, and the voltage detection unit detects a reference voltage between the reference wire and the feedback wire and compares the first detected voltage with the reference voltage. In the above aspect, the reference voltage varies along with the first detected voltage depending on the number of strings that contact the frets in parallel. Therefore, by comparing the first detected voltage with the reference voltage, the fret that contacts the first string can be identified with high accuracy, regardless of the number of strings that contact the frets in parallel.

[0157] In a specific example (Aspect 10) of Aspect 9, the reference voltage varies depending on the number of pressed strings among the plurality of strings. In the above aspect, the reference line is installed so that the reference voltage varies depending on the number of pressed strings among the plurality of strings. Therefore, as described above, the fret that contacts the first string can be identified with high accuracy regardless of the number of strings that contact the fret in parallel.

[0158] In a specific example (Aspect 11) of any one of Aspects 1 to 10, the instrument further includes a string-pressing analysis unit that identifies the string-pressing position on the first string in accordance with a change in the first detected voltage detected each time the drive signal is supplied. According to this aspect, the string-pressing position can be identified with high accuracy.

[0159] In a specific example (Aspect 12) of any of Aspects 1 to 11, a predetermined DC voltage is applied to each of the plurality of strings, and a string-pressing determination unit is further provided that determines whether or not a string is pressed based on the voltage of each of the plurality of strings. According to this aspect, it is possible to accurately determine whether or not a string is pressed based on the voltage of each string to which the DC voltage is applied.

[0160] In order to electrically or magnetically identify the fret that is in contact with the string among the multiple frets, a configuration is required for electrically connecting the multiple frets to wiring. In consideration of the above, a stringed instrument according to one aspect (Aspect A) of the present disclosure includes a neck, a fingerboard mounted on the neck, multiple conductive frets arranged on the fingerboard at intervals, multiple conductive strings that can contact any of the multiple frets, and wiring connected to each of the multiple frets.

[0161] A specific example of Aspect A (Aspect B) includes a wiring board installed between the neck and the fingerboard and a plurality of connection parts installed on the surface of the wiring board, the wiring being installed on the wiring board, each of the plurality of frets including a protrusion inserted into the fingerboard, each of the plurality of connection parts being connected to the protrusion of the fret corresponding to the connection part. According to the above aspect, the protrusion inserted into the fingerboard on each fret is connected to the connection part of the wiring board. Therefore, each fret can be electrically connected to the wiring using a simple configuration that does not require wiring.

[0162] In a specific example (Aspect C) of Aspect A, each of the plurality of connection portions is a flexible conductor that is deformed by being pressed by the protrusion. According to the above aspect, the plurality of frets and the wiring are electrically connected by the conductor compressed by the pressure from the protrusion. Therefore, even if there is an error in the position or size of each fret, the fret can be reliably connected to the wiring.

[0163] 100... electric bass, 10... body, 11... neck, 12... fingerboard, 13... head, 14_n (14_1 to 14_N)... frets, 15_m (15_1 to 15_5)... strings, 16... pegs, 17... bridge, 18... nut, 19... pickup, 20... wiring board, 20a... mounting surface, 21_n (21_1 to 21_N)... drive coil, 22... feedback line, 23... reference line, 24_n (24_1 to 24_N), 25_n (25_1 to 25_N)... connection part, 28_m (28_1 to 28_5)... detection coil, 3 0...detection device, 40...signal supply unit, 41_n (41_1 to 41_N)...drive circuit, 42...signal line, 43...capacitor, 44...low-pass filter, 45...resistance element, 46...capacitor, 47...common line, 48_k (48_1 to 48_K)...distribution circuit, 50...voltage detection unit, 51_m (51_1 to 51_5)...resistance element, 52_m (52_1 to 52_5)...detection unit, 53...output circuit, 54...reference unit, 55...signal output unit, 60A, 60B...string pressing analysis unit, 71...differential circuit, 72...amplification circuit.

Claims

1. A stringed instrument comprising: a neck; a plurality of conductive frets arranged at intervals along the neck; a plurality of conductive strings capable of contacting any of the plurality of frets; a plurality of drive coils respectively corresponding to the plurality of frets; a signal supply unit that supplies a drive signal to each of the plurality of drive coils; a feedback line connected to each of the plurality of frets; and a voltage detection unit that detects a first detected voltage between a first string of the plurality of strings and the feedback line during a period in which the drive signal is supplied to each of the plurality of drive coils.

2. The stringed instrument of claim 1, wherein the feedback wire is connected to a portion of the first string that is located closer to the tip of the neck than the multiple frets, and the first detected voltage is the voltage between the feedback wire and a portion of the first string that is located closer to the base of the neck than the multiple frets.

3. The stringed instrument of claim 1, wherein said plurality of strings includes a second string, said first string and said second string are connected to said feedback line, and said voltage detection unit includes a first detection circuit that detects said first detection voltage, and a second detection circuit that detects a second detection voltage between said second string and said feedback line.

4. The stringed instrument of claim 3, wherein the magnetic field generated in each of the plurality of drive coils is linked to a first detection coil including the first string and the feedback line, and a second detection coil including the second string and the feedback line.

5. The stringed instrument of claim 3, further comprising: a first resistor element connected between said feedback line and a portion of said first string that is located closer to the tip of said neck than said frets; and a second resistor element connected between said feedback line and a portion of said second string that is located closer to the tip of said neck than said frets.

6. The stringed instrument of claim 1, further comprising a fingerboard mounted on said neck, said plurality of frets being mounted on said fingerboard, said fingerboard being located between said first string and said feedback line, and said plurality of drive coils being located between said fingerboard and said feedback line.

7. A stringed instrument as claimed in claim 6, comprising: a wiring board placed between the neck and the fingerboard; and a plurality of connection parts placed on a surface of the wiring board, the plurality of drive coils and the feedback line being placed on the wiring board, each of the plurality of frets including a protrusion inserted into the fingerboard, and each of the plurality of connection parts being connected to the protrusion of a fret among the plurality of frets which corresponds to the connection part.

8. The stringed instrument according to claim 7, wherein each of the plurality of connection parts is a flexible conductor that is deformed when pressed by the protrusion.

9. The stringed instrument of claim 1, further comprising a reference wire that does not contact the plurality of frets, the reference wire extending along the neck and connected to the return wire, and the voltage detection unit detecting a reference voltage between the reference wire and the return wire, and comparing the first detected voltage with the reference voltage.

10. The stringed instrument according to claim 9, wherein the reference voltage varies depending on the number of pressed strings among the plurality of strings.

11. The stringed instrument according to claim 1, further comprising a string pressing analysis unit which identifies a pressing position on said first string in response to a change in said first detection voltage detected each time said drive signal is supplied.

12. The stringed instrument according to claim 1, further comprising a string pressing determination unit for applying a predetermined DC voltage to each of said plurality of strings and determining whether or not each of said plurality of strings is pressed in accordance with the voltage of said each of said plurality of strings.