Shepard Keyboard

[Maximizing Mobile Surface for Musical Expression]
Traditional mobile synthesizers often struggle with cramped interfaces by attempting to replicate multi-octave keyboards. The Shepard Keyboard takes a fundamentally different approach. By leveraging the "infinite pitch" nature of Shepard Tones, we have completely removed redundant octave keys. By reclaiming this valuable screen real estate, we have dedicated every available pixel to high-density expressive controls and tactile performance tools, allowing you to transform a limited mobile screen into a specialized musical interface.

[Detailed User Manual]
Master the infinite scale with our comprehensive visual guide:
https://docs.google.com/presentation/d/1fuiwogr7H3Mv6T7IUy5FcggWQ3p_RZXfCQXxu8idgj8/edit?usp=sharing

[Fact-Based Performance Controls]
- Vertical (Y-Axis) Expression: Assign and control parameters such as Volume, Vibrato, or Filter Cutoff in real-time based on the vertical touch position on each key.
- Horizontal (X-Axis) Slide Playing: Hold and slide across keys for smooth, guitar-like pitch transitions while maintaining a constant sound, ideal for glissando effects.
- Dual XY Pad Controllers:
- Pad 1 (Tone): Precise manipulation of Center Frequency and Frequency Gamma Range. Turn on the new "High Follow Mode" for artifact-free, extreme modulation when pushing the pad to its limits.
- Pad 2 (Filter): Real-time control of Low-Pass Filter (LPF) Cutoff Frequency and Resonance.
- Precision Sliders & Buttons: Dedicated controls for Modulation, Pitch Bend, Overdrive, and instant "Pseudo-Octave Jumps" to shift the frequency center.
- Expandable Interface: Collapse the control panels to expand the keyboard area, maximizing your focus on the performance.

[Immersive Performance Modes]
- Circular Keyboard: Experience the infinite scale through natural circular gestures for seamless, never-ending pitch movement.
- N-Octave Mode: Expand your harmonic reach by integrating 2-octave or 3-octave circular logic into the infinite scale. This feature successfully weaves multiple octaves into a continuous pitch illusion, while the number of keys dynamically shifts based on the selected octave count.
- Scale Configuration & Equal Temperaments: Remove black keys and evenly distribute specific scales like Pentatonic or Whole Tone. Turn on "Equal Temperament Mode" to reveal a slider setting the number of notes per octave, unlocking microtonal exploration from 5-EDO to 17-EDO.
- Basic Random Sequencer: A non-AI random playback feature. Set BPM, Note Value, and Note-On Probability, and let the app generate a completely random, endless stream of notes. While not traditionally "musical," this unpredictable sequence is highly effective for sleep induction or ambient soundscapes.

[Technical Specifications]
- Professional Audio Engine: Built using Google's Oboe (C++) for ultra-low latency tactile response.
- Adaptive DSP Engine & "High Follow" Mode: The core engine dynamically calculates only actively audible octaves, dramatically reducing CPU load and preserving battery life.
- Full Envelope Control: Precision ADSR settings with a "Fixed Duration" mode for percussive, glockenspiel-like tones.
- Customizable Audio Settings: Selectable Sample Rates and adjustable Buffer Sizes to balance performance and stability.

[Ideal For]
- Sound Designers: Creating seamless tension and "infinite" risers for cinema, games, or electronic music.
- Experimental Musicians: Exploring the boundaries of psychoacoustics and microtonal performance.
- Mobile Performers: Users requiring a stable, low-latency lead instrument with professional-grade gestural expression.

Developer's Note:
This instrument leverages professional-grade C++ audio libraries to minimize latency. By reclaiming the screen from unnecessary keys and dedicating it to Y-axis expression and intuitive XY pads, the Shepard Keyboard provides a unique platform to bring organic, evolving life to the mathematical beauty of the infinite scale.

Recent changes:
Optimized for Android 16 (API 36) for seamless performance
Implemented Multi Octave Mode
Implemented High Follow Mode
Add pad controls to random play
Implemented Basic Random Sequencer function
implemented Equal Temperament Edit function
filter pads has also been added to the circular keyboard mode screen.
Implement seamless key mode within circular key mode.
Fixed an issue in Android 12 where the sound would not play the moment you tapped.
Sample rate selection function.