Contrapunk

What it does

Contrapunk is a real-time polyphony, harmony, and improvisation companion that converts guitar input into MIDI and generates counterpoint harmony. It uses a voice-leading solver to pick the best legal next note for each voice, enforcing rules like no parallel fifths, no voice crossing, and encouraging contrary motion. The engine supports 4 counterpoint species (note-against-note, two-against-one, four-against-one, suspensions) and 7 harmony modes (e.g., Diatonic Thirds, Diatonic Fourths, Contrary Motion Stateful, Counterpoint Stateful). It also offers 3 voice-leading presets: Palestrina (16th-century strict species), Bach Chorale, and Jazz. The app includes a CLAP plugin host that allows routing harmony into external instruments without a DAW.

Who it is for

Contrapunk is designed for guitarists, composers, producers, and music theorists who want to explore counterpoint and harmony in real time. It is particularly useful for jazz guitarists, ambient producers, composition students, and DSP engineers. The app is free, open source, and available as a desktop app (macOS, Windows, Linux) or in the browser via WebAssembly. No account is required.

Why it matters

Contrapunk makes advanced counterpoint rules accessible to musicians without requiring deep music theory knowledge. It provides instant feedback and creative inspiration, allowing users to play a single note and hear a full four-voice harmony. The sub-10ms latency ensures real-time performance. By being open source, it invites customization and educational use, such as checking species-counterpoint homework or building DAW plugins.

Launch signal

Contrapunk was launched on Hacker News as a Show HN post titled "Contrapunk – Real-time counterpoint harmony from guitar input." The website indicates version 1.2.0 is current, with earlier versions 1.0.0 and Proteus. The app is actively maintained with a GitHub repository and community testimonials from musicians and engineers.

Brand and naming

The name "Contrapunk" is a portmanteau of "counterpoint" and "punk," suggesting a rebellious or modern take on classical counterpoint. It is memorable and distinctive, though it coincidentally shares a name with a 1970s Indonesian progressive rock band. The brand positions itself as a free, open-source tool for real-time harmony generation, appealing to both traditional music theorists and experimental musicians.