Browser-based stem export tool for the Teenage Engineering OP-XY.
Automates the process of bouncing individual stems from your OP-XY by controlling mute/unmute via MIDI, recording USB audio, and packaging the results as WAV files — all from your browser.
No DAW required. No installs. Just Chrome + USB-C.
- Connect your OP-XY via USB-C
- Select which tracks to export and configure settings
- Bounce — StemBounce mutes all tracks, then solos each one in sequence, playing the song and recording the audio output
- Download individual WAV stems or a ZIP bundle
Each stem is automatically aligned to beat 1 using MIDI Clock sync, so you can drag and drop straight into your DAW.
- Automatic stem isolation — MIDI CC mute/unmute on each of the 8 tracks
- MIDI transport control — Start/Stop via System Realtime messages
- Beat-1 alignment — Uses MIDI Clock to precisely trim pre-roll so all stems start on the downbeat
- BPM auto-detection — Reads tempo from OP-XY MIDI Clock
- Full mix pass — Optionally record a mix of all selected tracks
- 24-bit/48kHz or 16-bit/44.1kHz output
- ZIP packaging — Download all stems in one click with BPM in filenames
- Real-time audio meter — Visual feedback during recording
- MIDI diagnostics panel — Debug transport, mute, and raw MIDI messages
StemBounce needs three MIDI settings enabled on your OP-XY. Without these, the app can't control playback or mute tracks.
- On your OP-XY, press
COM - Press
M3to enter the devices view - You'll see toggles for clock, notes, and other (CCs) — make sure the following are enabled:
| Setting | What to enable | Why |
|---|---|---|
| Clock | Send on | So StemBounce can detect your BPM and align stems to beat 1 |
| Notes | Receive on | Standard MIDI communication |
| Other (CCs) | Receive on | So StemBounce can mute/unmute individual tracks via CC 9 |
- Press
M3again to see page 2 of MIDI device settings — make sure transport receive is enabled so the OP-XY responds to Start/Stop commands
- OP-XY connected via USB-C (not just charging — use a data cable)
- COM → M3: Clock send = on
- COM → M3: Other (CCs) receive = on
- COM → M3 → M3: Transport receive = on
- Using Chrome (Firefox/Safari don't support Web MIDI)
Tip: If StemBounce connects but the OP-XY doesn't play or tracks don't mute, 99% of the time it's one of these settings. The MIDI diagnostics panel at the bottom of the configure screen can help you debug — try the START and Mute buttons to test.
- React 19 + TypeScript
- Vite
- Zustand (state management)
- Web MIDI API (MIDI control)
- Web Audio API (audio capture via ScriptProcessorNode)
- JSZip (client-side ZIP)
- Zero backend — runs entirely in the browser
npm install
npm run devOpen http://localhost:5173 in Chrome (Web MIDI API requires Chrome).
npm run build
npm run previewRequires Chrome 43+ (or any Chromium-based browser) for Web MIDI API support. Firefox and Safari do not support Web MIDI.
Built by OM3 and Claude (Anthropic).
Design inspired by Teenage Engineering's visual language.
MIT
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