Electronic Keyboard Channel Routing for Acoustic Piano Resonance

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Solution Overview

Problem

Existing electronic keyboard instruments struggle to simulate the resonance sound of an acoustic piano faithfully, particularly in generating damper resonance and string resonance, due to limitations in feedback mechanisms and dynamic assignment methods.

Innovation Solution

An electronic keyboard instrument with a hardware and software configuration that includes dynamic and static assignment methods for string and stroke sound channels, utilizing closed loop circuits and feedback mechanisms to generate damper resonance by turning off dampers for specific notes, and combining string and stroke sound outputs to mimic acoustic piano resonance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dynamic assignment method is used for string and stroke sound channels, then sound quality and resonance simulation are improved, but device complexity and processing overhead increase

Engineering Contradiction:
Improveresonance sound simulation accuracyVSAvoidhardware and software configuration complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the keyboard into multiple octave ranges (e.g., lower octave, middle octave, upper octave) and assigns different resonance generation methods to each segment. For example, the lower octave may use full dynamic assignment with feedback mechanisms, while upper octaves use simplified static assignment, thereby reducing overall system complexity while maintaining resonance accuracy where most needed.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different resonance generation strategies are applied to different pitch regions based on their acoustic characteristics. Lower pitch notes receive more complex processing with feedback loops and multiple resonators, while higher pitch notes use simpler generation methods, matching the local acoustic requirements of each region and reducing unnecessary complexity.

Inventive Principle:
Principle #3Local quality

2Reliability

If feedback mechanisms are implemented for damper resonance generation, then damper resonance quality is improved, but processing time and computational load increase

Engineering Contradiction:
Improvedamper resonance generation accuracyVSAvoidprocessing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

Resonance parameters, feedback coefficients, and filter settings are pre-calculated and stored in memory before runtime. When a key is pressed or the damper is engaged, the system retrieves these pre-computed parameters and applies them immediately, avoiding real-time complex calculations while maintaining accurate damper resonance generation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The feedback mechanism dynamically adjusts resonance parameters based on real-time playing conditions such as key velocity, sustained note duration, and damper position. This allows the system to optimize processing by applying feedback only when and where needed, rather than continuously for all notes, thereby reducing overall processing time while maintaining resonance accuracy during critical moments.

Inventive Principle:
Principle #15Dynamics

3Reliability

If multiple resonators are assigned to each key and pitch, then resonance sound fidelity is improved, but device complexity and resource requirements increase

Engineering Contradiction:
Improveresonance sound fidelityVSAvoidresonator configuration complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

A small set of resonators is designed to serve multiple keys and pitches through dynamic assignment and cross-modulation. Each resonator can be assigned to different pitches at different times based on the active notes and octave range, allowing the same physical resonator resources to simulate resonance for multiple keys, thereby reducing the total number of resonators needed while maintaining fidelity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The resonators use dynamically adjustable parameters such as frequency, damping coefficient, and resonance width that can be changed in real-time based on the assigned pitch and playing context. This allows a single resonator to accurately simulate different pitches and resonance characteristics by parameter modulation rather than requiring separate fixed-frequency resonators for each key.

Inventive Principle:
Principle #35Parameter changes

4Device complexity

If static pairing of resonators to keys and pitches is used, then device complexity is reduced, but resonance sound accuracy and adaptability deteriorate

Engineering Contradiction:
Improveresonator assignment simplicityVSAvoidresonance response adaptability
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The resonator assignment system transitions from static to dynamic pairing based on real-time playing conditions. When notes are sustained or when the damper is engaged, resonators are dynamically reassigned to active pitches, allowing the system to adapt resonance responses to actual playing context while maintaining simpler hardware architecture through controlled dynamic behavior rather than full complexity.

Inventive Principle:
Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively generates resonance sounds that closely resemble those of an acoustic piano, providing improved sound quality and simplifying hardware structure by stabilizing note generation and reducing the need for dynamic assignment.

Implementation Method 1

utilizing closed loop circuits and feedback mechanisms to generate damper resonance

Methodology Applied
Scientific EffectFeedback: Feedback

Implementation Method 2

provides a set of 88 resonators with corresponding output gain multipliers, each statically paired to a specific key and pitch

Methodology Applied
Scientific EffectResonance: Resonance

Data Source

PatentEP3882906B1Electronic keyboard musical instrument and method of generating musical sound
Publication Date: 2025.08.27 CASIO COMPUTER CO LTD
  • EP3882906B1 patent drawingFigure 1
  • EP3882906B1 patent drawingFigure 2
  • EP3882906B1 patent drawingFigure 3

AI summary

An electronic keyboard musical instrument includes a sound source (13C) configured to, in response to detection of key-pressing of the first key in damper-off detection, input first excitation signal data (s61) corresponding to the first key to a first channel (63), input first channel output data (s35) which is output from the first channel (63) to each of low-register channels (21-01 to 21-12) corresponding to the respective low-register keys, and output musical sound data which is generated based on respective pieces of low-register channel output data which is output from the respective low-register channels (21-01 to 21-12) and the first channel output data (s35), as musical sound data corresponding to the first key.