This is a modular MIDI synthesizer that can run either as a standalone Windows application or on a Teensy microcontroller.

Features

General

• Mono (for now)
• Unlimited polyphony
• MIDI-controlled
• Most parameters can be modulated in real time by the output of any module
• Any arbitrary arrangement of modules & is possible, with automatical signal generation ordering

Oscillators

• Sine, sawtooth, square, triangle oscillators
• White noise
• Custom waveforms (.wav file required)
• Performed (with MIDI input) and LFO-type oscillators

Performance

• Mono legato and portamento

Effects

• ADSR
• LFOs
• Filters (RBJ): high/low/allpass, bandpass, notch, high/low shelf
• Chorus
• Flanger
• Phaser
• Delay
• Reverb: Schroeder, Luff
• Distortion: arctan soft clip, linear ("ideal") wavefolder, Serge wavefolder

Codebase

• AVX2 and AVX512 for vector arithmetic
• Eigen (Windows) & CMSIS-DSP (Teensy) for linear algebra
• TeensyAudio for Teensy audio output (not used for the signal processing itself)
• RtMidi for Windows MIDI input
• PortAudio for Windows audio output

Building

Requires C++20.

For desktop: build with MicrocontrollerSynth.sln.

For Teensy: build with PlatformIO and see PlatformIO.ini. Use the TEENSY flag if not using PlatformIO. MIDI input pins are configurable.

I have dependencies in ../libraries/include/, ../libraries/lib/Debug, and ../libraries/lib/Release. These paths can be reconfigured in the Visual Studio project. Maybe one day I will turn this into a proper CMake project.

Usage

All configurations are found in src/utils/config.h.

To set up the synthesizer, edit src/applications.cpp to set up all modules, map midi CC, and route their inputs & outputs (in this step they can be made modular and made to be modulated by other modules). Everything is compile-time and will most likely stay that way.

MIDI keyboard required. For Windows, just plug it into USB, and the application will automatically detect the first input device.

To use a custom oscillator, place the .wav file containing one period of the waveform in resources/waveforms/{bitrate}_bit/{sample_rate}/. In src/applications.cpp, create an Oscillator object with the extensionless filename as the argument. There is a .wav generator script at other/wav_generator.ipynb.

Hardware Setup

My setup (very simple): Teensy 4.1, Teensy Audio Shield, a USB module routing into the audio shield's USB ports (will replace), audio output device plugged into the audio shield's headphone jack.

Plan to add physical knobs & sliders, maybe also a keyboard.