Show HN: Contrapunk – Real-time counterpoint harmony from guitar input, in Rust

11 hours ago

Contrapunk is a real-time MIDI harmony generator and guitar-to-MIDI converter that ensures proper counterpoint rules.
It operates with sub-10ms latency, making it suitable for live performances, and is built in Rust.
The tool is free, requires no login, and works in Chrome browsers with any MIDI controller.
Features include an 8-mode harmony engine with historical rules, 28 scale modes, and deterministic voicing.
Guitar input allows real-time pitch detection, onset tracking, and auto-calibration for converting guitar playing to counterpoint.
Latency is minimized through single-cycle detection, 2-frame voting, and 128-sample buffers.
Contrapunk runs on multiple platforms: native desktop via Tauri, browsers via WebAssembly, and server mode for studios, all using the same Rust core.
Voice leading features enforce music theory rules, such as rejecting parallel fifths, preventing voice crossing, and applying spacing rules.
It is open source under the MIT license, aiming to make centuries of music theory knowledge accessible to all musicians.

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