A generative Euclidean rhythm sequencer that runs entirely in your browser.
Make music to share, export or remix. Presets so you don't need to know everything — just start creating.
Instead of expensive DAWs, subscription limits, or hours searching for the right loop — Rondel gives you a usable beat in seconds. Pick a preset, tweak it, export as WAV or MIDI. It's yours. No account, no install, no copyright worries.
The sequencer uses Euclidean rhythms — a mathematical way of spacing beats as evenly as possible. The same patterns found in West African djembe, Cuban tresillo, and countless other musical traditions. You don't need to know any of this — the presets handle it — but it's why everything sounds musical instead of random.
rondel.reprodev.com — Open on any device. Works on phone, tablet, and desktop.
Pick a preset from the sidebar, hit play, change the key — export when you're happy. Everything synthesised in real-time with Web Audio.
| Feature | Details |
|---|---|
| 🎹 Voices | 30 synthesised instruments (Web Audio, zero samples) |
| 🎛️ Presets | 75 curated across 5 categories |
| 📤 Export | WAV (any duration) + MIDI (4 bars) |
| 🎵 Key/Scale | 15 keys × 9 scales |
| ⏱️ BPM | 40–200, adjustable live |
| 🔵 Rings | 5 concurrent Euclidean rhythm layers |
| 🔗 Sharing | URL-encoded patch state — share with one link |
| 📱 Mobile | Fully responsive with bottom sheet UI |
| 📦 Dependencies | Zero. Pure ESM, no build step |
- Content creators — background music without copyright strikes
- Rappers and producers — quick beat ideas, loop material, MIDI to drop into your DAW
- Non-musicians — make something without music theory
- Students — explore generative music and Euclidean rhythms
- Anyone — who wants a beat fast without opening a DAW
- Zero friction — no install, no signup, no download
- Platform agnostic — phone, tablet, laptop. No powerful machine needed
- Lightweight — no RAM-heavy DAW, just a web page
- You own it — everything you export is yours, no subscription limits
- WAV + MIDI — drop the MIDI into Ableton, GarageBand, FL Studio, whatever you use
- 30 instruments — drums, bass, melodic, pads, vocal textures. Assign any to any ring
- Share links — URL recreates your exact patch. Send it to anyone
Every patch encodes into a URL. Copy it, send it to a friend — they open the exact same groove with all your settings intact. No account needed.
Master volume slider in the header with mute toggle. Adjusts in real-time through the compressor/limiter chain so nothing clips regardless of how many voices are stacked.
Nine drum/percussion voices (kick, snare, hat, clap, tom, cowbell, rim, conga, shaker), eleven melodic voices (bass, sub bass, poly, pluck, bell, kalimba, vibraphone, marimba, metallic, sitar, organ), and ten pad/vocal textures (pad, string pad, gong, tape, choir, vocal pad, vocal stab, harmonies, whisper, vocal glitch). All synthesised — no samples, no loading times.
Change the musical key and scale with one click. 15 root notes × 9 scales (major, minor, dorian, phrygian, lydian, mixolydian, pentatonic, blues, chromatic). Melodic voices follow your selection automatically.
Export WAV at any duration (15s to 10 minutes) for a finished audio file, or export MIDI (4 bars) to drop into your DAW for further production. Filenames include preset name, BPM, key, and timestamp so you can tell them apart.
New users get a quick 3-step onboarding that explains the interface without overwhelming. Dismisses permanently after completion.
Type to filter across all 75 presets instantly. Categories with no matches hide automatically so you only see what's relevant.
Bottom sheet drawer, sticky search, touch-friendly canvas interaction, and a compact transport bar. Full functionality on phone — not a stripped-down version.
Open index.html in any modern browser. That's it.
Serving over HTTP gives the best timing accuracy (Web Worker clock). Opening the file directly still works — the app falls back to a standard timer automatically.
git clone https://github.com/reprodev/rondel.git
cd rondel
npm start
# → http://localhost:3000docker build -t rondel .
docker run -p 3000:3000 rondel
# → http://localhost:3000# Python
python3 -m http.server 3000
# npx
npx serve .- Push this repo to GitHub
- Settings → Pages → Deploy from branch →
main→/ (root) - Live at
https://yourusername.github.io/rondel
All paths are relative — works on any subpath. The Dockerfile, package.json, and test files don't affect the site.
Connect the repo. No build command. Publish directory: . (root). Deploys on push.
- Pick a preset — browse by category or search by name
- Hit play — press Space or click the play button
- Make it yours — change key, scale, BPM, swap instruments
- Edit patterns — click rings on the canvas to add/remove beats
- Export — WAV for audio, MIDI for your DAW, or copy a share link
rondel/
├── index.html ← The app (HTML + CSS + inline script)
├── serve.js ← Zero-dependency dev server
├── package.json ← npm start/test scripts
├── Dockerfile ← Containerised deployment
├── src/
│ ├── audio/ ← 30 voice synths, scheduler, master chain, export
│ ├── ui/ ← Canvas renderer, interactions, controls
│ ├── gen/ ← Euclidean algorithm, scales, melody generation
│ └── state/ ← Patch schema, 75 presets, URL codec
├── test/ ← 263 unit tests across 14 files
└── README.md
- Pure JavaScript (ES modules)
- Web Audio API for synthesis
- Canvas 2D for radial visualisation
- No framework, no bundler, no dependencies
- Node.js only needed for local dev server and tests
npm test263 tests across 14 test files covering all pure modules.
Getting music for a project shouldn't be hard. Whether you need a background beat for a video, a loop to rap over, or a MIDI file to drop into your DAW — the usual path involves expensive software, subscription limits, or hours searching.
Rondel was built out of that frustration. The creator wanted a quick way to generate a beat as a MIDI and WAV file while working on sampling vocal tracks. Instead of spending hours in a full DAW just to get a rhythm bed, Rondel gives you something usable in seconds — so you can focus on the creative work that actually matters.
MIT — this project is open-source. Fork it, remix it, build on it, make it your own.
All audio you export is yours — no attribution required for the music you create.
This project was built using Kiro IDE:
- Steering — Project context loaded into every session
- Spec-driven development — Requirements → Design → Tasks workflow
- Collaborative authoring — All code written in partnership with Kiro
- Iterative development — Visible in commit history from first synth to final polish
🎵 The rhythm is yours.
Built using Kiro for the Ready, Spec, Ship 2026 Hackathon by codingagents.fyi — Sponsored by Kiro