Synth

A portable C synth engine with a desktop host for realtime audio and MIDI control.

Synth is organized around a reusable engine in include/synth/ and src/, plus a desktop app in platform/desktop/ that connects the engine to miniaudio and PortMidi. The goal is to keep the audio engine portable while still making it easy to play, test, and experiment from a regular computer.

Highlights

• Portable C99 synth engine
• 12-voice polyphony
• ADSR envelope, pitch bend, master gain, and musical note operations
• Spectral bandlimited wavetable oscillator
• Sine, saw, square, and continuous waveform morphing
• Two oscillator controls with level, morph, pitch, fine-tune, octave, and stereo spread
• Low-pass filter with variable intensity
• Global morphable LFO with 52 signed parameter routes
• Saturation, distortion, bitcrusher, flanger, ring mod, chorus, EQ, delay, plate reverb, and compressor
• Desktop audio playback through miniaudio
• Optional MIDI input and controller mapping through runtime-loaded PortMidi

Quick Start

Configure the development build:

cmake --preset dev

Build the desktop synth, MIDI monitor, and tests:

cmake --build --preset dev

Start the desktop app from the repository root:

cmake --build --preset dev --target run_synth

With no MIDI controller connected, the app plays a default test note until you press Enter. With a MIDI input source connected, the app starts silent and waits for MIDI notes.

Bind MIDI controls:

cmake --build --preset dev --target midi_monitor
./build/dev/midi_monitor learn --output config/midi/my_keyboard.conf
./build/dev/synth --midi-config config/midi/my_keyboard.conf

Run commands from the repository root so relative config paths resolve to config/midi/.

In the learn prompt, type list to see synth parameters, then use bind <name|number> and move a knob, fader, or other control on your MIDI keyboard. Type save when you are done. More detail is available in MIDI controller mapping.

Requirements

• A C99 compiler
• CMake 3.21 or newer
• macOS, Linux, or Windows with a CMake-supported C compiler
• Windows: Visual Studio 2022 is supported through the vs2022 preset
• Optional: PortMidi for MIDI input

miniaudio is vendored under third_party/miniaudio/. PortMidi is loaded dynamically at runtime, so the project still builds when PortMidi is not installed.

On macOS, PortMidi can be installed with:

brew install portmidi

On Windows, copy portmidi.dll into the same folder as synth.exe, or pass --portmidi-path. With the Visual Studio preset, the debug executable lives under build/vs2022/Debug/.

On macOS or Windows, pass --portmidi-path followed by the full path of the PortMidi library file:

# macOS
./build/dev/synth --portmidi-path /custom/path/libportmidi.dylib

# Windows PowerShell
.\build\vs2022\Debug\synth.exe --portmidi-path "C:\custom\path\portmidi.dll"

The PORTMIDI_PATH environment variable remains available as an alternative. A command-line path takes precedence over the environment variable. The custom path is tried first, followed by the normal platform locations. Without an available PortMidi library, the synth still runs, but MIDI input is disabled.

Common Commands

cmake --preset dev                         # configure a debug build
cmake --build --preset dev                 # build app, tools, and tests
ctest --preset dev                         # run the test suite
cmake --build --preset dev --target run_synth
cmake --build --preset dev --target run_midi_monitor
cmake --preset release                     # configure an optimized build

Project Layout

Path	Purpose
include/synth/	Public synth engine headers
src/	Portable synth engine implementation
src/effects/	Portable post-filter effects
src/internal/	Private engine helpers and wavetable internals
platform/desktop/	Desktop audio app, miniaudio adapter, and MIDI input
config/midi/	Controller mapping files
tools/	Developer utilities such as the MIDI monitor
tests/	C test programs run through CTest
third_party/	Vendored or reserved third-party dependencies
platform/teensy/	Reserved for a future Teensy 4.1 port

Documentation

• Engine notes
• LFO API and destination contract
• Desktop app usage
• MIDI controller mapping
• Tools
• Tests

Status

The synth currently focuses on a portable engine, a simple desktop host, and MIDI-driven experimentation. Future platform work can build on the same engine without pulling desktop audio or MIDI dependencies into the core.