Contrapunk is an open-source tool designed for real-time polyphony, harmony generation, and improvisational support, with a particular focus on guitar-to-MIDI conversion. It serves as a companion for musicians interested in exploring counterpoint, harmony, and live musical interaction, offering features that automatically generate harmonies and counterpoint lines in real time as notes are played. The platform emphasizes strict voice-leading rules and supports up to four voices, making it suitable for both creative performance and educational purposes.
The tool provides a variety of harmony and counterpoint modes, including Palestrina, Bach chorale, jazz voicings, and several species of counterpoint such as note-against-note, two-against-one, four-against-one, and suspensions. Contrapunk enforces classical compositional rules, such as rejecting parallel fifths and voice crossing while encouraging contrary motion and stepwise motion in its generated harmonies. It offers seven harmony modes and supports 57 different scales, giving users a wide palette for experimentation. The engine can process live guitar input with sub-10ms latency, converting plucked notes directly into MIDI for immediate harmony generation.
Contrapunk is available in multiple formats. Users can run it as a native desktop application on macOS, Windows, or Linux, or use it directly in a web browser via a WebAssembly-based version. The desktop version supports hosting CLAP plugins in-app, allowing users to route generated harmonies into virtual instruments without requiring a separate digital audio workstation. The browser version provides WebMIDI output for integration with DAWs and hardware. The tool is built with Rust, Tauri, and WebAssembly technologies, and its source code is openly available for modification, research, or building derivative works.
The platform is completely free to use and does not require an account. Its open-source nature encourages musicians, composers, educators, and developers to adapt or extend its functionality. Contrapunk positions itself as a real-time MIDI harmony generator and guitar-to-MIDI converter within the broader class of music and audio software.
Contrapunk is a Music & audio product. It focuses on generating real-time harmonies and converting guitar input to MIDI for musicians and composers. Contrapunk is an open-source project aimed at musicians and composers. The project is open source (MIT). The product ships for the web and macOS.
Contrapunk first shipped in 2025. The project is developed in the open on GitHub with 74 stars and 443 commits in the last 90 days. Among its 5 catalogued features are real-time harmony, guitar-to-MIDI, and polyphony support.
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