Play a single note on your guitar. Before it decays, three more voices appear—not stacked in thirds like a chorus pedal, not harmonizing by rote interval arithmetic, but moving according to rules that governed music composition when the Baroque era was still news.
That's the premise behind Contrapunk, an open-source harmony generator that applies centuries-old voice-leading principles in real time. Think of it as algorithmic counterpoint for the digital age, though whether it represents genuine innovation or an elaborate theory exercise depends largely on whom you ask.
The software emerged from Vibhav Bobade, a developer based in Bangalore, during an ADCx music hackathon. Its first major release drew attention on Hacker News, accumulating 100 points and sparking 40 comments within sixteen hours—respectable numbers for a niche music tool, though hardly viral territory. The project is MIT licensed, free to use, and carries no venture backing or commercial ambitions. Just one developer scratching a particular itch.
The Technical Promise
Unlike the interval-based harmonizers that have populated guitar pedalboards for decades—your Electro-Harmonix Intelligent Harmony Machine, your TC Electronic Quintessence—Contrapunk attempts something conceptually different. Where those devices add a third or fifth above your melody line, this software generates independent voices constrained by rules designed to prevent parallel fifths, voice crossing, and spacing violations. It's species counterpoint rendered as live performance infrastructure.
The architecture runs on Rust, with desktop builds using Tauri v2 and a browser version compiled to WebAssembly. Bobade claims the native macOS build achieves sub-10 millisecond latency through 128-sample buffers and a two-frame pitch voting system. "Works really well for higher notes," he noted in the Hacker News thread, adding almost as an afterthought: "bass not so much right now."
That qualification matters. Pitch detection from monophonic guitar input has challenged developers for years, and low-frequency notes remain particularly problematic. The admission suggests Contrapunk inherits those limitations even as it attempts to build something more sophisticated on top.
You run a direct input from your instrument into an audio interface. The software detects pitch and onset timing, then generates MIDI notes following one of eight harmony modes—diatonic thirds, strict counterpoint, Barry Harris-style bebop voicings. Those MIDI signals can trigger any virtual instrument in your DAW. Simple signal chain, ambitious processing.
Voice-Leading as Feature Set
The software bundles four distinct compositional styles: Palestrina, Bach Chorale, Jazz, and Free. Each applies different scoring algorithms when the harmony engine evaluates possible notes. Choose Bach Chorale and you get controlled spacing and tendency tone resolution—the sound of 18th-century German hymnody. Switch to Jazz and the engine permits more adventurous intervals, chromatic motion.
Beyond rule sets, Contrapunk adds timing jitter, velocity variation, swing adjustments. The humanization features attempt to solve a problem that's plagued algorithmic composition since MIDI became ubiquitous: quantized perfection sounds robotic. The README lists multiple presets, though the randomization remains deterministic enough to reproduce results across sessions. That's either a feature or a limitation depending on whether you value consistency or surprise.
Twenty-eight scale modes span five families. The engine maintains state across your performance, remembering recent voicing choices to ensure smooth motion rather than unpredictable leaps. It's the sort of detail that suggests careful thinking about musical context, not just note generation.
What You Can Actually Download
The release includes a macOS DMG. Windows and Linux builds appear on the roadmap but haven't materialized—a familiar pattern for solo open-source projects where ambition outpaces available development time. Bobade acknowledged the limitation plainly in a Reddit post to r/musictheory: "currently only supported for the mac."
There's also a browser version at contrapunk.fly.dev, adding worklet overhead compared to the native build but offering a try-before-you-download option. Both versions run the same Rust DSP core. Whether the browser experience delivers the same sub-10ms performance Bobade claims for the native build remains unclear from public documentation.
GitHub issues sketch out community requests. Users want VST and AU plugin versions for tighter DAW integration. They're asking for rhythm-aware triggers that sync harmony changes to beat detection. One proposal investigates SonoBus integration for what Bobade calls "Contrapunk Cloud"—potentially enabling ensemble performance over network connections, though that seems several steps removed from the current reality.
More immediate concerns also surface. Issue #14 tracks a bug where MIDI output fails for some users. The repository includes over 280 tests covering the audio pipeline, but early adopters are finding edge cases the test suite missed.
The Competitive Landscape (Such As It Is)
Guitarists have had audio-to-MIDI conversion for years. Jam Origin's MIDI Guitar plugins and Fishman's TriplePlay hardware system both offer polyphonic tracking with DAW integration. Contrapunk bundles that conversion with harmony generation in a single package—simpler signal chain, but also less flexibility if you want to swap out components.
The differentiation comes from the counterpoint engine itself. Hardware harmonizers calculate harmony by adding fixed intervals or staying within a chosen scale. Contrapunk treats each generated voice as an independent melodic line following rules about how voices should move in relation to one another.
That's conceptually different, even if the sonic results won't always make the distinction obvious. For musicians interested in species counterpoint exercises or exploring historical composition techniques through improvisation, the tool offers something closer to an interactive theory workbook. For those who just want usable harmony parts—backing tracks for a recording session, live texture for a performance—the practical question becomes whether the latency holds up and whether voice-leading constraints produce more musical results than simpler approaches.
Perhaps more importantly: does anyone actually want counterpoint as a live performance tool? The question hangs unanswered.
Documentation Gaps and Open Questions
Published latency benchmarks don't exist yet, at least not in public-facing documentation. Sample recordings that demonstrate the sub-10ms claim in practice are similarly absent. The demo video in the repository runs under three megabytes but doesn't show the tool in full production context—just proof of concept, essentially.
The project's homepage at contrapunk.com returned 502 errors during recent access attempts. Cached snapshots show older messaging about "improvisation focused node based audio processing" and a waitlist, suggesting the web presence hasn't caught up to the release cycle. The GitHub repository at contrapunk-audio/contrapunk serves as the definitive source for now.
For developers interested in the implementation, ENGINE_DEEP_DIVE.md offers substantial technical detail. The code is public, the license permissive. If you want to understand or extend the system, the building blocks are available.
What Happens Next
The real test for Contrapunk isn't whether it implements counterpoint algorithms correctly—the test suite suggests it does—but whether musicians actually use it. Open-source music tools live or die on community adoption. Even technically impressive projects can languish if they solve problems nobody had or introduce workflow friction that outweighs their benefits.
Bobade has built something technically ambitious with no obvious commercial angle. Whether counterpoint becomes a standard technique in the guitarist's toolkit or remains a curiosity for theory enthusiasts, Contrapunk demonstrates that the algorithmic challenges have solutions.
Mac users can download the DMG and experiment. Everyone else can try the browser build or wait. The question isn't whether the software works—it apparently does, within stated limitations—but whether it matters.
And that's a question only musicians, in studios and bedrooms and practice spaces, can answer.
