peterc/coopiano

Source: https://github.com/peterc/coopiano

coopiano - physically modelled piano synthesizer

https://github.com/user-attachments/assets/aa7c3835-e664-40b2-91cd-c30ee46f2247

A physically modelled piano synthesizer in C++17. It renders notes and MIDI files to stereo WAV and supports live MIDI input on macOS. Sound is synthesized from a hammer, string, soundboard and sympathetic-resonance model, with a room reverb effect. No piano samples, downloads or third-party libraries are required.

It is VERY EARLY days for releasing this code. The piano is fine, but I have a prototyped AU and VST plugin, etc. which are not part of this open release so far.

Build

You need a C++17 compiler and Make. On macOS, install the Xcode Command Line Tools (xcode-select --install) if they are not already available, then run:

make
./coopiano --help

macOS builds link the system CoreMIDI, AudioToolbox, CoreFoundation and CoreAudio frameworks. The source also supports offline rendering on other platforms with a C++17 compiler and threads; live MIDI/audio is macOS-only. This extraction was built and tested on macOS; other platforms have not been verified here.

Compiler settings can be overridden, for example make CXX=clang++ CXXFLAGS=-O3. Run make clean before changing compiler settings. make clean removes only the executable, preserving any renders and presets.

Run

# Note, velocity, duration, optional key-hold time (seconds)
./coopiano A4 0.5 8
# Writes A4_gp.wav; quote sharp note names, e.g. 'G#3'.

# Built-in musical demo; writes demo_piano.wav
./coopiano demo

# Render your own MIDI file; no MIDI files are bundled
./coopiano performance.mid 1.0 performance.wav

# Play from connected MIDI sources or the virtual coopiano MIDI destination
./coopiano live
# macOS only; Ctrl-C to stop

Running ./coopiano without arguments renders A4 at velocity 0.5 for eight seconds. Offline commands write 44.1 kHz, 16-bit stereo WAV files; they do not play them automatically. On macOS, use afplay A4_gp.wav to listen. Each offline render is peak-normalized independently.

Presets

Built-in defaults work without any configuration file. default.ini documents the available voicing and reverb controls, including their ranges. Copy it, edit the copy, then select it explicitly:

cp default.ini my-piano.ini
./coopiano --preset my-piano.ini live
./coopiano --preset my-piano.ini audition --output audition.wav

The audition command plays a chord at increasing velocities. Use --help for its chord, velocity and timing options. Editing default.ini alone does not change the built-in sound; pass --preset and restart playback to load changes.

GP_NO_REVERB=1 ./coopiano A4 0.5 8
GP_SAVE_SETTINGS=1 ./coopiano --preset my-piano.ini A4 0.5 8

GP_SAVE_SETTINGS=1 writes a resolved preset beside the WAV as A4_gp.wav.ini. Environment overrides take precedence over preset settings.

Source layout

• coopiano.cpp: CLI, MIDI file parser, WAV writer and macOS live host.
• piano.hpp: header-only synthesis library in namespace piano.
• instrument.hpp: voice pool, note/pedal scheduling and instrument effects.
• streaming_soundboard.hpp: streaming soundboard convolution.
• preset.hpp and reverb.hpp: INI configuration and stereo room effect.
• piano_host.hpp and piano_resampler.hpp: host-rate adaptation and resampling.
• live_diagnostics.hpp and live_bench.hpp: support compiled into the macOS host.

The C++ source/header files originate from the development project. Historical comments may refer to documentation in that larger project. The original test and benchmark collections are not bundled here.

License

MIT. See LICENSE.