ESP32-S3 FM Drum Synth

A high-performance FM drum synthesizer built for the ESP32-S3.
Supports multi-operator FM synthesis, realtime MIDI control, patch editing via OLED+encoder UI, and flexible drumkit management.

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✨ Features

• ✅ 6-operator FM synthesis with 17 extendable routing algorithms
• ✅ Custom envelope engine with hold, fast-release, and block-aware processing
• ✅ Stereo audio output via I2S, using normalized float-to-int audio pipeline
• ✅ Per-note drumkits with full patch mapping to GM MIDI notes (128-note map)
• ✅ Real-time MIDI control (USB or serial), including velocity and retriggers
• ✅ On-device GUI via SH1106 OLED + rotary encoder + buttons
• ✅ Waveform blending: sine, triangle, square, saw, noise, and inverted variants
• ✅ Nonlinear SVF filter with drive per voice
• ✅ Per-voice reverb send, globally editable reverb parameters
• ✅ Optimized DSP math: fast sine, LUTs, fast_fabsf, saturators, etc.
• ✅ Extremely low latency voice allocator with note stealing and MAX_VOICES_PER_NOTE control
• ✅ Drumkit save/load via JSON on SD (or LittleFS, configurable)
• ✅ Modular architecture: patching, voice engine, allocator, GUI, and storage are decoupled

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🧠 Architecture Overview

Each FmVoice6:
    - 6x FmOperator
    - Flexible routing (17 algorithms)
    - Filter + envelope
    - Reverb send

Each FmOperator:
    - Multiple waveforms
    - Separated fmProcess(), amProcess(), outProcess()
    - Internal feedback

a demo recording Demo MP3