A new open-source tool called Contrapunk generates real-time counterpoint harmony from guitar input using Rust. The browser-based application converts guitar playing into MIDI with sub-10ms latency, making it suitable for live performance. Built with a Rust core, it runs everywhere—native desktop via Tauri, browser via WebAssembly, and server mode for studios.

Contrapunk implements proper counterpoint rules including Palestrina and Bach styles, with 8 harmony modes and 28 scale options. The system features deterministic voicing, parallel fifths rejection, voice crossing prevention, and spacing rules—essentially centuries of music theory encoded in software. Guitar input uses real-time pitch detection, onset tracking, and auto-calibration to ensure accurate conversion.

The project is MIT licensed and free with no login required. It works in Chrome with any MIDI controller, making it immediately accessible to musicians. By combining classical music theory with modern real-time processing in a cross-platform Rust application, Contrapunk represents a novel approach to bridging traditional composition techniques with digital music creation.