Breath control circuitry for electronic instruments

Abstract

Methods, apparatuses, and systems are disclosed. In one example, an apparatus may comprise a pressure sensor configured to receive a pressure-based input and generate a pressure-sensor voltage based on the pressure-based input. The apparatus may further comprise a breath-adjustment circuit comprising a plurality of operational amplifiers. The breath-adjustment circuit may be configured to receive the pressure-sensor voltage as input, generate an output voltage based on the pressure-sensor voltage, and provide the output voltage to an external electronic musical instrument such that audio produced by the electronic musical instrument is influenced via the pressure-based input.

Description

BREATH CONTROL CIRCUITRY FOR ELECTRONIC INSTRUMENTS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional patent application no. 63 / 746,877, filed January 17, 2025, which is hereby incorporated by reference in its entirety.BACKGROUND

[0002] The term “breath controller” may generally refer to devices that may be used to convert pressure resulting from air movement (e. ., caused by inhaling, exhaling, or other air movement produced via a user’s lungs, lips, teeth, tongue, palate, cheeks, larynx, etc.) into electronic control signals. Such control signals may be converted into Musical Instrument Digital Interface (MIDI) messages which may then be supplied to a synthesizer or another device which a user intends to control in some way via a breath controller.SUMMARY

[0003] Systems and methods for breath controllers are provided herein.

[0004] In an example, a breath-adjustment circuit may comprise a first operational amplifier configured to receive a first voltage as input and buffer the first voltage to generate a buffered voltage.

[0005] The breath-adjustment circuit may further comprise a second operational amplifier configured to generate, based on the buffered voltage, a second voltage that satisfies a shiftfactor condition and a range condition. The shift-factor condition may be configured via a first resistor associated with the second operational amplifier. The range condition may be configured via a second resistor associated with the second operational amplifier.

[0006] The breath-adjustment circuit may further comprise a third operational amplifier configured to generate, based on the second voltage and an inverted input for the third operational amplifier, a third voltage. The inverted input for the third operational amplifier may be connected to a first gang of a dual-gang rheostat.

[0007] The breath-adjustment circuit may further comprise a fourth operational amplifier configured to generate, based on a first bias voltage and an inverted input for the fourth operational amplifier, a coordinated corrective shift-factor voltage. The inverted input for the fourth operational amplifier may be connected to a second gang of the dual-gang rheostat.

[0008] The breath-adjustment circuit may further comprise a fifth operational amplifier configured to generate a summed voltage based on the third voltage and the coordinated corrective shift-factor voltage.

[0009] The breath-adjustment circuit may further comprise a sixth operational amplifier configured to generate a span-setting voltage based on a second bias voltage. The span-setting voltage may be configured via a resistor associated with the sixth operational amplifier.

[0010] The breath-adjustment circuit may further comprise a seventh operational amplifier configured to generate an output voltage based on the summed voltage and the span-setting voltage.

[0011] In another example, an apparatus may comprise a pressure sensor configured to: receive a pressure-based input and generate a pressure-sensor voltage based on the pressure-based input.

[0012] The apparatus may further comprise a breath-adjustment circuit comprising a plurality of operational amplifiers. The breath-adjustment circuit may be configured to receive the pressuresensor voltage as input, generate an output voltage based on the pressure-sensor voltage, and provide the output voltage to an external electronic musical instrument such that audio produced by the electronic musical instrument is influenced via the pressure-based input.

[0013] The external electronic musical instrument may comprise a synthesizer.

[0014] The pressure-based input may be based on airflow or air pressure to which the pressure sensor is exposed.

[0015] The plurality of operational amplifiers may comprise a plurality of voltage summers.

[0016] The plurality of operational amplifiers may comprise a plurality of inverting amplifiers.

[0017] The breath-adjustment circuit may further comprise a dual-gang rheostat. The breathadjustment circuit may be further configured to: generate the output voltage based on the pressure sensor voltage and a user-adjustable input of the dual-gang rheostat.

[0018] In another example, an apparatus may comprise a pressure sensor configured to: receive a pressure-based input and generate a pressure-sensor voltage based on the pressure-based input.

[0019] The apparatus may further comprise a first breath-adjustment circuit comprising a first plurality of operational amplifiers. The first breath-adjustment circuit may be configured to receive the pressure-sensor voltage and generate a first output voltage based on the pressuresensor voltage.

[0020] The apparatus may further comprise a second breath-adjustment circuit comprising a second plurality of operational amplifiers. The second breath-adjustment circuit may be configured to receive the pressure-sensor voltage and generate a second output voltage based on the pressure-sensor voltage.

[0021] The apparatus may further comprise a voltage-controlled filter configured to receive the first output voltage and an audio signal and generate a filtered audio signal based on the first output voltage and the audio signal.

[0022] The apparatus may further comprise a voltage-controlled amplifier configured to receive the second output voltage and the filtered audio signal, generate an output audio signal based on the second output voltage and the filtered audio signal, and provide the output audio signal to an external electronic musical instrument such that audio produced by the electronic musical instrument may be influenced (e.g, controlled and / or manipulated) via the pressure-based input.

[0023] The first breath-adjustment circuit may be further configured to provide the first output voltage to an additional electronic musical instrument such that audio produced by the additional electronic musical instrument may be influenced via the pressure-based input.

[0024] The second breath-adjustment circuit may be further configured to provide the second output voltage to an additional electronic musical instrument such that audio produced by the additional electronic musical instrument may be influenced via the pressure-based input.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 illustrates a circuit diagram of an example breath-adjustment circuit that allows the gain and offset of a voltage from a pressure sensor to be manipulated independently of each other, according to one example described herein.

[0026] FIG. 2 illustrates a block diagram that depicts examples of how breath-adjustment circuits described herein may be utilized to provide multiple independently controllable breath control signals from a single source of air pressure, according to one example.

[0027] FIG. 3 depicts an apparatus that serves as one illustrative example of how the apparatus of FIG. 2 may be implemented, according to one example.

[0028] FIG. 4 illustrates a flow diagram of actions that a circuit may perform in accordance with examples described herein.DETAILED DESCRIPTION

[0029] In general, modern commercial breath controllers that are capable of controlling an external synthesizer utilize MIDI. Such a commercial breath controller may, for example, be used by feeding a voltage produced by a pressure sensor e.g., in response to air pressure) into an analog-to-digital converter (ADC) and then using a digital device (e.g., a microcontroller) to transmit that data (e.g., indicated via the output of the ADC in response to receiving the voltage produced by the pressure sensor as input) in a format that conforms to MIDI control specifications e.g., as MIDI continuous control (MIDI CC)). This approach may be relatively inexpensive and easy to implement.

[0030] Despite the low cost and ease of implementation, there are a number of technical challenges that impede the performance of modern breath controllers and therefore result in lackluster performance of such breath controllers in practice.

[0031] For example, MIDI protocol supports a relatively low data transfer rate (e.g., 31.25 kilobits per second (kbps) in classic MIDI) compared to many modern protocols that are used for electronic communication. As examples for comparison, Ethernet (1GBASE-T) supports up to one gigabit per second (Gbps) and Universal Serial Bus (USB) 3.0 supports up to five gigabits per second (Gbps).

[0032] Given this relatively low data transfer rate, an engineer designing a MIDI breath controller is either forced to sacrifice fidelity of the breath control signal or to raise the rate at which MIDI messages are transmitted and thereby to risk overloading a target synthesizer (e.g., a synthesizer that receives the breath control signal) with an influx of data that the target synthesizer was not meant to handle. Even at the maximum MIDI baud rate of 31250 (31,250 bits of information per second), the breath control signal produced by MIDI breath controllers is not smooth or continuous enough. As a result, digital artifacts (often described as “zipping”) can often be heard in audio that is controlled via MIDI breath controllers. This may oblige the designer of the target synthesizer to apply some form of interpolation to incoming breath controlled data (e.g., breath control signal) to mitigate such artifacts. If such interpolation is not implemented in the target synthesizer, the target synthesizer will likely not be compatible with MIDI breath control (e.g. , because audio produced via the target synthesizer using the breath control signal would be of unsatisfactory quality).

[0033] Thus, although digital signal processing has advanced far enough that digital breath control is theoretically possible, manufacturers’ ubiquitous use of MIDI as the data transfer protocol for electronic musical instruments has made breath control a relatively impractical possibility with existing devices.

[0034] Early breath controllers utilized analog breath control to control external devices. The Lyricon® Wind Synthesizer Driver from the early 1970s, the Yamaha® BC1, and the Steiner-Krumar Master’s Touch™ are examples of such early breath control devices. However, these early breath control devices are also hampered by technical challenges (e.g., compatibility constraints, lack of independent adjustability of certain parameters, etc.). For instance, the Lyricon® Wind Synthesizer Driver predated the MIDI protocol and therefore cannot be used with the majority of modem synthesizers. The Yamaha® BC1 was designed to plug into a proprietary “breath” mini jack found on a proprietary type of synthesizer (e.g, a CS-01 Analog synthesizer) and lacked the ability to manipulate incoming sound sources. The Steiner-Krumar Master’ s Touch™ does not allow an amplifier and a filter to be controlled independently of each other.

[0035] Systems and methods described herein address the technical challenges that hamper existing breath controllers by using a direct analog approach that produces sonically pleasing results without undesirable artifacts. In addition, systems and methods described herein are compatible with a broad range of musical instruments and allow various aspects of a breath control signal, such as gain and offset, to be controlled independently of one other. Furthermore, in some examples, systems and methods described herein may be used to produce, from a single breath source, a plurality of breath control signals whose respective gains and respective offsets can be controlled independently of each other. Each breath control signal may be used to control a different device, respectively. For instance, in some examples, systems and methods described herein may produce two breath control signals (e.g, based on a pressure-sensor voltage captured via a pressure sensor) that may be used to control a filter and an amplifier, respectively.

[0036] In some examples, the systems and methods described herein may facilitate using breath control to manipulate a sound source and / or a control voltage.

[0037] In some examples, systems and methods described herein may be incorporated into and / or performed via circuits and / or devices. Such a circuit and / or device may be implemented as a standalone device and / or incorporated into an instrument (e.g., an electronic musical instrument). For example, if systems and / or methods described herein are implemented via astandalone device, a user may utilize any combination of wired (e.g., an auxiliary (AUX) cable, a USB cable, etc.) and / or wireless hardware (e.g., antennas, etc.) to transmit an input audio signal e.g., from a computing device) to the standalone device. The user may then blow into the standalone device (e.g., on, over, across, and / or at a pressure sensorthat the standalone device comprises). By blowing into the standalone device, the user may alter the tone and / or volume of an output audio signal that the standalone device produces based on the input audio signal. The output audio signal may be a version of the input audio signal that has been manipulated (e.g., altered) based on one or more breath control signals that the pressure sensor produces in response to the blowing. In some examples, the one or more breath control signals may comprise one or more respective control voltage outputs. In some examples, the one or more respective control voltage outputs may be provided to (e.g., transmitted, via wired and / or wireless hardware) to a synthesizer that comprises a control voltage input such that the synthesizer may be controlled via the user’s breath (e.g., blowing). In some examples, these functions (e.g., altering the tone and volume of an audio signal controlling the synthesizer) may be performed concurrently (e.g., simultaneously) or separately.

[0038] In some examples, if a device that implements systems and / or methods described herein is incorporated into an instrument (e.g., an electronic musical instrument), the instrument may utilize an oscillator to send an audio signal through the device. In some examples, the instrument may comprise, or be operably coupled to, a mouthpiece that directs the air into the pressure sensor (which the device may comprise) and allows manipulation of the internal oscillator.

[0039] FIG. 1 illustrates a circuit diagram of an example breath-adjustment circuit 100 that allows the gain and offset of a voltage from a pressure sensor to be manipulated independently of each other, according to one example described herein.

[0040] The breath-adjustment circuit 100 comprises operational amplifiers 102, 104, 106, 108, 110, 112, 114 that are connected in the manner shown.

[0041] The operational amplifier 102 may be configured as a voltage follower (e.g., a buffer amplifier or a unity-gain buffer). The operational amplifier 102 may receive a pressure-sensor voltage (e.g., a voltage produced by a pressure sensor in response to being exposed to air pressure, airflow, and / or a pattern of change therein) as input. As output, the operational amplifier 102 may output a buffered voltage (e.g., buffers the received pressure-sensor voltage). The buffered voltage may match the pressure sensor voltage, but provide a stronger drivecapacity such that the buffered voltage may be able to drive a load that pulls more current than could be driven by the pressure-sensor voltage without causing voltage sagging. The operational amplifier 102 may serve to isolate the signal source (e.g, the pressure sensor in this example) from the load.

[0042] In addition to receiving the pressure-sensor voltage as an input, the operational amplifier 102 may receive the buffered voltage produced by the operational amplifier 102 as input (e.g, an inverting input).

[0043] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 102 may comprise a TL072 U1A (e.g, the first operational amplifier (section A) of a TL072 dual operational amplifier integrated circuit designated as Ul). Persons of skill in the art will also recognize that other types of operational amplifiers may also be configured to function in the manner ascribed to the operational amplifier 102 without departing from the spirit and scope of this disclosure.

[0044] The operational amplifier 104 may receive the buffered voltage as input and may produce a second voltage that satisfies a shift-factor condition and a range condition. The range condition may comprise, for example, the condition that the difference between an upper-bound voltage value and a lower-bound voltage value matches (e.g., equals) a predefined value, wherein the upper-bound voltage value and the lower-bound voltage value may define an interval that defines the set of possible values of the second voltage. The shift-factor condition may comprise, for example, the condition that the interval is positioned at a particular place in a coordinate system used to represent possible voltage values.

[0045] For example, if the buffered voltage lies within a first interval of possible voltage values (e.g., where the first interval of possible voltage values may be defined as the possible voltage values that the pressure sensor is physically capable of outputting), the operational amplifier 104 may implement a function that projects (e.g, maps) the buffered voltage into a second interval of possible voltage values. The range of the second interval (e.g., the difference between the upperbound voltage value and the lower-bound voltage value for the second interval) may be greater than, less than, or equal to the range of the first interval. In addition, the second interval may or may not overlap with the first interval. In some examples, the operational amplifier 104 may implement a linear mapping of the first interval to the second interval (e.g., such that the lower-bound voltage value of the first interval maps to the lower-bound voltage value of the secondinterval, the upper-bound voltage value of the first interval maps to the upper-bound voltage value of the second interval, the voltage value at the center of the first interval maps to the voltage value at the center of the second interval, etc.).

[0046] The operational amplifier 104 may amplify (e.g., increase the range of possible voltage values) or attenuate (e.g., decrease the range of possible voltage values) the buffered voltage to account for a voltage range (e.g., which may be indicated by the possible voltage values that the pressure sensor is physically capable of outputting) that may have to be adjusted. In addition, the operational amplifier 104 may add a shift factor) to the buffered voltage to compensate for the position of a lower bound of the possible voltage values that the pressure sensor is physically capable of outputting (e.g., if that lower bound does not match a desired lower bound for the buffered voltage) .

[0047] This function that the operational amplifier 104 implements may serve as a gain stage that sets a minimum voltage shift factor (e.g., to achieve the desired lower bound for the buffered voltage) and / or a desired voltage change at a maximum breath pressure (e.g., that may be indicated by the buffered voltage matching an upper-bound voltage value that the pressure sensor is physically capable of outputting) by changing the values of the resistors 104a-d. In some examples, the voltage shift factor may be adjusted by adjusting the resistance of the resistors 104a, 104b. In some examples, the gain may be adjusted by adjusting the resistance of the resistors 104c, 104d.

[0048] In an example, in which the pressure-sensor voltage that is output by a pressure sensor ranges from 0.2 volts (e.g., at a minimum pressure that the pressure sensor is capable of detecting) and 4.7 volts (e.g., at a maximum pressure that the pressure sensor is capable of detecting), the first interval of possible voltage values would be defined as [0.2, 4.7], If the desired lower bound for the buffered voltage is -5 volts and the desired voltage change (e.g., range) is 10 volts at maximum breath pressure, this gain stage allows the desired lower bound for the desired voltage and the desired voltage change to be achieved (e.g., by mapping the buffered voltage into the second interval of possible voltage values defined as [-5, 5]). Persons of skill in the art will recognize that, in other examples, the first interval of possible voltage values and the second interval of possible voltage values may have different lower bounds, different upper bounds, and / or different ranges without departing from the spirit and scope of this disclosure.

[0049] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 104 may comprise a TL072 U1B (e.g., the second operational amplifier (section B) of a TL072 dual operational amplifier integrated circuit designated as Ul). Persons of skill in the art will also recognize that other types of operational amplifiers may also be configured to function in the manner ascribed to the operational amplifier 104 without departing from the spirit and scope of this disclosure.

[0050] The operational amplifier 106 may function as an inverting amplifier that has a first gang of a dual -gang rheostat 106a connected to the output of the operational amplifier 106 and to an inverting input of the operational amplifier 106 to provide attenuation of the magnitude of the change of the voltage. The operational amplifier 106 may work in conjunction with the operational amplifier 108, which may comprise a potentiometer 108a (e.g., a trimmer) connected to a voltage (e.g., a bias voltage) and ground via an inverting input of the operational amplifier 108. The potentiometer 108a may form a resistor divider that may provide a variable voltage. This variable voltage may then be run through an inverting amplifier configuration in which a second gang of the dual-gang rheostat 106a is connected to the output of the operational amplifier 108 and to the inverting input of the operational amplifier 108.

[0051] When the first gang of the dual -gang rheostat 106a is connected as shown, as the resistance of the first gang (which is connected across the operational amplifier 106) decreases, the shift factor of the signal is attenuated to zero. As a result, in the example described above in which the desired lower bound of a desired interval of possible voltage values is -5 volts, as the dual-gang rheostat 106a is adjusted (e.g., via turning of a knob, moving of a slider, etc.) to adjust the first gang to a minimum resistance, the lower-bound voltage will rise to zero. To compensate for this voltage rise, the second gang of the as the dual -gang rheostat 106a (which is connected across the operational amplifier 108) is connected such that, as the second gang is adjusted to a maximum resistance, the voltage output of the operational amplifier 108 increases to 5 volts. This ensures that the lower-bound voltage (e.g., the lower-bound value of the interval of possible voltage values) is stable even when the magnitude of the voltage change (e.g., the range of the possible voltage values) is attenuated.

[0052] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 106 may comprise a TL072 U2B (e.g., the second operational amplifier (section B) of a TL072 dual operational amplifier integrated circuit designated as U2). Persons of skill in the artwill also recognize that other types of operational amplifiers may also be configured to function in the manner ascribed to the operational amplifier 106 without departing from the spirit and scope of this disclosure.

[0053] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 108 may comprise a TL072 U2A (e.g., the first operational amplifier (section A) of a TL072 dual operational amplifier integrated circuit designated as U2). Persons of skill in the art will also recognize that other types of operational amplifiers may also be configured to function in the manner ascribed to the operational amplifier 108 without departing from the spirit and scope of this disclosure.

[0054] The operational amplifier 110 may comprise a voltage summer that adds the voltages that are output by the operational amplifiers 106, 108. The voltage output by the operational amplifier 110 in response to receiving the voltages output by the operational amplifiers 106, 108 may maintain a constant lower-bound voltage as the dual -gang rheostat 106a is adjusted even though the magnitude of the voltage range changes in response to the adjustment to the dual-gang rheostat 106a.

[0055] As indicated above, the operational amplifier 106 may allow gain to be adjusted via adjustment of the dual-gang rheostat 106a. For instance, the dual-gang rheostat 106a may comprise a user-adjustable input such as a knob or a slider that allows resistance of the first gang and the second gang to be adjusted. If the user-adjustable input comprises a knob, for example, the gain may be adjusted by rotating the knob about an axis (e.g., the angular position of the knob may be used to set the resistance of the dual-gang rheostat 106a). If the user-adjustable input comprises a slider, the gain may be adjusted by moving the slider within a track e.g., the position of the slider within the track may be used to set the resistance of the dual-gang rheostat 106a). Other types of user-adjustable inputs may also be used. The operational amplifier 108 may generate a coordinated corrective voltage shift-factor voltage that, when added to the voltage output by the operational amplifier 106 via the operational amplifier 110, ensures that the lower bound does not drift as the gain is adjusted.

[0056] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 110 may comprise a TL072 U4A (e.g., the first operational amplifier (section A) of a TL072 dual operational amplifier integrated circuit designated as U4). Persons of skill in the art will also recognize that other types of operational amplifiers may also be configured to functionin the manner ascribed to the operational amplifier 110 without departing from the spirit and scope of this disclosure.

[0057] The operational amplifier 112 may comprise an inverting amplifier in which a voltage (e.g., a bias voltage) is run through a rheostat 112a (e.g, which may be implemented via a trimmer). The rheostat 112a may function as a voltage divider that sets the span of the overall voltage offset (e.g., the range of possible voltage offset values). For example, if the desired set of possible voltage values for the offset is defined by the interval [-5, 5], the voltage that is run through the rheostat 112a would be 10 volts (e.g., because the upper-bound offset voltage of 5 volts minus the lower-bound offset voltage of -5 volts would be ten volts). A rheostat 112b may be connected across the operational amplifier 112 to allow for attenuation of the voltage that is output by the operational amplifier 112 (e.g., such that the value of the offset may be adjusted via a user-adjustable input that the rheostat 112b comprises, such as a knob or a slider).

[0058] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 112 may comprise a TL072 U3A (e.g, the first operational amplifier (section A) of a TL072 dual operational amplifier integrated circuit designated as U3). Persons of skill in the art will also recognize that other types of operational amplifiers may also be configured to function in the manner ascribed to the operational amplifier 112 without departing from the spirit and scope of this disclosure.

[0059] The operational amplifier 114 may comprise a voltage summer that adds the voltages that are output by the operational amplifiers 110, 112. The voltage output by the operational amplifier 114 in response to receiving the voltages output by the operational amplifiers 110, 112 may serve as the final output voltage of the breath-adjustment circuit 100. This final output voltage may be used as a control voltage for a voltage-controlled amplifier, a voltage-controlled filter, and / or an external device (e.g., such as an external electronic musical instrument).

[0060] As shown in the example depicted by the breath-adjustment circuit 100, the operational amplifier 114 may comprise a TL072 U4B (e.g., the second operational amplifier (section B) of a TL072 dual operational amplifier integrated circuit designated as U4). Persons of skill in the art will also recognize that other types of operational amplifiers may also be configured to function in the manner ascribed to the operational amplifier 114 without departing from the spirit and scope of this disclosure.

[0061] FIG. 2 illustrates a block diagram 200 that depicts examples of how breath-adjustment circuits described herein (e.g., such as the breath-adjustment circuit 100 of FIG. 1) may be utilized to provide multiple independently controllable breath control signals from a single source of air pressure (e.g., breath source), according to one example.

[0062] An apparatus 210 may comprise a breath-adjustment circuit 212 and a breath-adjustment circuit 214. The breath-adjustment circuit 212 and the breath-adjustment circuit 214 may be similar and / or identical to the breath-adjustment circuit 100 described above with respect to FIG.1. The breath-adjustment circuit 212 and the breath-adjustment circuit 214 may allow independent control over a voltage-controlled filter 216 and a voltage-controlled amplifier 218, respectively (e.g., via outputs of the breath-adjustment circuit 212 and the breath-adjustment circuit 214).

[0063] The apparatus 210 may further comprise a pressure sensor 220 that may output a pressure-sensor voltage. The pressure-sensor voltage may be transmitted (e.g., sent via a wired or wireless connection) to both the breath-adjustment circuit 212 and the breath-adjustment circuit 214 as indicated via the arrows 221a, 221b. The voltage output from the breath-adjustment circuit 212 may be buffered as a potential output to an external instrument (e.g., as indicated via the arrow 213a) and may also be transmitted to the voltage-controlled filter 216 (e.g., as indicated via the arrow 213b) to be used as a control voltage therefor. The voltage output from the breath-adjustment circuit 214 may be buffered as a second potential output to an external instrument (e.g., as indicated via the arrow 215a) and may also be transmitted to the voltage-controlled amplifier 218 (e.g., as indicated via the arrow 215b) to be used as a control voltage therefor.

[0064] The voltage-controlled filter 216 may receive an audio signal as input (e.g., as indicated via the arrow 217a) and generate a filtered audio signal (e.g., a filtered version of the audio signal in accordance with the control voltage received from the breath-adjustment circuit 212). The filtered audio signal may be transmitted to the voltage-controlled amplifier 218 (e.g., as indicated via the arrow 217b).

[0065] The voltage-controlled amplifier 218 may receive the filtered audio signal as input and generate an amplified-filtered audio signal (e.g., amplified version of the filtered audio signal in accordance with the control voltage received from the breath-adjustment circuit 214) as indicated via the arrow 219. The amplified-filtered audio signal may comprise an output voltage (e.g., ofthe apparatus 210) that may serve as a final audio output that has been modulated via the pressure sensor 220.

[0066] FIG. 3 depicts an apparatus 300 that serves as one illustrative example of how the apparatus 210 of FIG. 2 may be implemented, according to one example. Persons of skill in the art will recognize that the apparatus 300 is merely illustrative and that many other examples of how the apparatus 210 of FIG. 2 may be implemented are possible without departing from the spirit and scope of this disclosure.

[0067] The apparatus 300 as shown is being run on +12 / -12 volt supplies. The breath adjustment circuits 320a, 320b are positioned on the right side of the breadboard 310. The voltage-controlled amplifier 330 is positioned near the center of the breadboard 310. In this example, the voltage-controlled amplifier 330 is built around a voltage-controlled-amplifier integrated circuit as shown. The voltage-controlled filter 340 is positioned on the left side of the breadboard 310 and is utilizing control voltage inputs from the two potentiometers 350a, 350b (near the top of the breadboard 310) that are connected to 12 volts and ground. The two potentiometers 350a, 350b modulate the resonance and cutoff filters of the voltage-controlled-filter integrated circuit that the voltage-controlled filter 340 comprises. Near the bottom of the breadboard 310 are amplifiers that buffer an incoming voltage from a pressure sensor (not shown) and an audio signal coming from an external device.

[0068] FIG. 4 illustrates a flow diagram 400 of actions that a circuit may perform in accordance with examples described herein. In some examples, some of the actions depicted by the blocks shown in the flow diagram 400 may be performed in an order other than the order shown in the flow diagram 400. In addition, in some examples, actions depicted by some of the blocks shown in the flow diagram 400 may be omitted and / or actions not depicted by the blocks shown in the flow diagram 400 may be performed. Furthermore, in some examples, actions depicted by multiple blocks shown in the flow diagram 400 may be combined and / or divided.

[0069] As shown in block 402, a circuit may receive a first voltage as input. In some examples, the first voltage may be received from a pressure sensor. Furthermore, in some examples, the first voltage may be received via a first operational amplifier that the circuit comprises.

[0070] As shown in block 404, the circuit may buffer the first voltage to generate a buffered voltage. In some examples, the circuit may generate the buffered voltage via the first operational amplifier.

[0071] As shown in block 406, the circuit may generate, based on the buffered voltage, a second voltage that satisfies a shift-factor condition and a range condition. In some examples, the circuit may generate the second voltage via a second operational amplifier. In some examples, the shiftfactor condition may be configured via a first resistor associated with the second operational amplifier. Furthermore, in some examples, the range condition may be configured via a second resistor associated with the second operational amplifier.

[0072] As shown in block 408, the circuit may generate, based on the second voltage and a first inverted input that is connected to a first gang of a dual-gang rheostat, a third voltage. In some examples, the circuit may generate the third voltage via a third operational amplifier and the first inverted input may be received via the third operational amplifier.

[0073] As shown in block 410, the circuit may generate, based on a first bias voltage and a second inverted input connected to a second gang of the dual-gang rheostat, a coordinated corrective shift-factor voltage. In some examples, the circuit may generate the coordinated corrective shift-factor voltage via a fourth operational amplifier.

[0074] As shown in block 412, the circuit may generate a summed voltage based on the third voltage and the coordinated corrective shift-factor voltage. In some examples, the circuit may generate the summed voltage via a fifth operational amplifier.

[0075] As shown in block 414, the circuit may generate a span-setting voltage based on a second bias voltage. In some examples, the circuit may generate the span-setting voltage via a sixth operational amplifier. Furthermore, in some examples, the span-setting voltage may be configured via a resistor associated with the sixth operational amplifier.

[0076] As shown in block 416, the circuit may generate an output voltage based on the summed voltage and the span-setting voltage. In some examples, the circuit may generate the output voltage via a seventh operational amplifier.

Claims

CLAIMS:

1. A breath-adjustment circuit comprising:a first operational amplifier configured to:receive a first voltage as input,and buffer the first voltage to generate a buffered voltage;a second operational amplifier configured to:generate, based on the buffered voltage, a second voltage that satisfies a shiftfactor condition and a range condition, wherein the shift-factor condition is configured via a first resistor associated with the second operational amplifier and the range condition is configured via a second resistor associated with the second operational amplifier;a third operational amplifier configured to:generate, based on the second voltage and an inverted input for the third operational amplifier, a third voltage, wherein the inverted input for the third operational amplifier is connected to a first gang of a dual-gang rheostat;a fourth operational amplifier configured to:generate, based on a first bias voltage and an inverted input for the fourth operational amplifier, a coordinated corrective shift-factor voltage, wherein the inverted input for the fourth operational amplifier is connected to a second gang of the dual-gang rheostat;a fifth operational amplifier configured to:generate a summed voltage based on the third voltage and the coordinated corrective shift-factor voltage;a sixth operational amplifier configured to:generate a span-setting voltage based on a second bias voltage, wherein the spansetting voltage is configured via a resistor associated with the sixth operational amplifier; anda seventh operational amplifier configured to:generate an output voltage based on the summed voltage and the span-setting voltage.

2. An apparatus comprising:a pressure sensor configured to:receive a pressure-based input, andgenerate a pressure-sensor voltage based on the pressure-based input; anda breath-adjustment circuit comprising a plurality of operational amplifiers, wherein the breath-adjustment circuit is configured to:receive the pressure-sensor voltage as input,generate an output voltage based on the pressure-sensor voltage, andprovide the output voltage to an external electronic musical instrument such that audio produced by the external electronic musical instrument is influenced via the pressure-based input.

3. The apparatus of claim 2, wherein the external electronic musical instrument comprises a synthesizer.

4. The apparatus of claim 2, wherein the pressure-based input is based on airflow or air pressure to which the pressure sensor is exposed.

5. The apparatus of claim 2, wherein the plurality of operational amplifiers comprises a plurality of voltage summers.

6. The apparatus of claim 2, wherein the plurality of operational amplifiers comprises a plurality of inverting amplifiers.

7. The apparatus of claim 6, wherein the breath-adjustment circuit further comprises a dualgang rheostat, and wherein the breath-adjustment circuit is further configured to:generate the output voltage based on the pressure-sensor voltage and a user-adjustable input of the dual-gang rheostat.

8. An apparatus comprising:a pressure sensor configured to:receive a pressure-based input, andgenerate a pressure-sensor voltage based on the pressure-based input;a first breath-adjustment circuit comprising a first plurality of operational amplifiers, wherein the first breath-adjustment circuit is configured to:receive the pressure-sensor voltage, andgenerate a first output voltage based on the pressure-sensor voltage;a second breath-adjustment circuit comprising a second plurality of operational amplifiers, wherein the second breath-adjustment circuit is configured to:receive the pressure-sensor voltage, andgenerate a second output voltage based on the pressure-sensor voltage;a voltage-controlled filter configured to:receive the first output voltage and an audio signal, andgenerate a filtered audio signal based on the first output voltage and the audio signal; anda voltage-controlled amplifier configured to:receive the second output voltage and the filtered audio signal,generate an output audio signal based on the second output voltage and the filtered audio signal, andprovide the output audio signal to an external electronic musical instrument such that audio produced by the external electronic musical instrument is influenced via the pressure-based input.

9. The apparatus of claim 8, wherein the first breath-adjustment circuit is further configured to:provide the first output voltage to an additional electronic musical instrument such that audio produced by the additional electronic musical instrument is influenced via the pressure-based input.

10. The apparatus of claim 8, wherein the second breath-adjustment circuit is further configured to:provide the second output voltage to an additional electronic musical instrument such that audio produced by the additional electronic musical instrument is influenced via the pressurebased input.

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