Deterministic audio workstation. Browser-native. Zero install.
Dual decks, Rust/Wasm DSP, WebGPU visuals, 19 instruments, automixer, beatmatching, 17 skins, MIDI, headphone cue.
Launch in Browser · Download Desktop · Website · Discussions
macOS (ARM64).dmg |
macOS (Intel).dmg |
Windows.exe |
Linux.AppImage |
Browser Zero install |
MIXI is a dual-deck DJ engine and step sequencer that runs entirely inside a web browser. The DSP pipeline runs in Rust/Wasm (AudioWorklet) or falls back to hand-wired Web Audio API nodes. No Tone.js. No third-party audio wrappers. No server required.
Load two tracks. Mix them. The groovebox runs in parallel on its own bus. The automixer watches phase, spectrum, and headroom on a 50ms tick and applies corrections as visible, non-destructive mutations. Plug in a MIDI controller and it maps to anything. Pick one of 17 skins or write your own in pure CSS.
It ships as a static site. It also packages as an Electron desktop app for macOS, Windows, and Linux. An optional Python sidecar handles heavier analysis offline.
Deck A/B (Track mode):
BufferSource → Trim → 3-Band Parallel Isolator EQ (LR4 24dB/oct)
→ ColorFX → DeckFX [FLT|DLY|REV|PHA|FLG|GATE]
├── Fader → Crossfader → MasterBus
└── CueGain → HeadphoneBus
Deck A/B (TurboKick mode):
KickSynth (pitch/decay/click/drive) → ValveA (tube) → ValveB (punch)
→ Filter+LFO → Delay → Rumble (dark reverb + sidechain pump)
→ DeckChannel.input → EQ → Fader → MasterBus
Deck A/B (TurboBass mode):
MainOsc (saw/pulse) + SubOsc (sine, -1oct) → PreFilterHP (44Hz)
→ Drive (tanh) → DiodeLadder (4-pole AudioWorklet, tanh saturation)
↑ FilterLFO (BPM-synced) ↑ FilterEnv (bipolar, accent-modulated)
→ VCA (2ms attack) → Dry + Distortion (Rat asymmetric)
→ Delay (BPM-synced, HP feedback) → Bus (reverb, chorus, limiter)
→ DeckChannel.input → EQ → Fader → MasterBus
EQ Crossover (Linkwitz-Riley):
Trim → LP₁→LP₂(250Hz) → lowGain → merge
Trim → HP₁→HP₂(250Hz) → LP₃→LP₄(4kHz) → midGain → merge
Trim → HP₃→HP₄(4kHz) → highGain → merge
Kill = gain 0. Other bands 100% unaffected.
MasterBus:
Gain → MasterFilter → BandSplit (300Hz crossover)
├── Sub (<300Hz) → Mono Sum (phase-safe for PA)
└── High (>300Hz) → Oversampled tanh Waveshaper
→ Parallel Compressor (gain-compensated) → DC Blocker (10Hz)
→ Headroom Pad (-0.3dB) → Brickwall Limiter → destination
HeadphoneBus:
CueSum + MasterTap → Mix knob → Level → destination
Split mode: Master → R ear | Cue → L ear
Wasm DSP Path (optional, toggle in Settings):
Source A → Trim → AudioWorklet input[0] ─┐
Source B → Trim → AudioWorklet input[1] ──┤→ Rust DSP Engine
DspEngine: Deck EQ → ColorFX → FX → Fader → Crossfader
→ Master: Filter → Distortion → Punch → Predictive Limiter → DC Blocker
← 128 samples @ 44.1kHz, ~10µs per block (99.6% headroom)
EQ is a parallel 3-band isolator with Linkwitz-Riley 24dB/oct crossovers (two cascaded Butterworth per crossover point). Flat magnitude sum at crossover, zero phase difference between bands. Kill on any band silences only that band — other bands completely unaffected.
The Rust DSP engine (mixi-core) runs the full signal chain in an AudioWorklet when enabled: per-deck EQ, color filter, 5 effects, fader, crossfader mixing, master filter, distortion, parallel compression, predictive limiter (0.2ms lookahead), and DC blocker. Parameters flow via a 512-byte SharedArrayBuffer with layout versioning.
The brickwall limiter (threshold -0.5dB, ratio 20:1, attack 1ms) guarantees the output never exceeds 0dBFS regardless of how the faders are handled.
The fastest way to install the desktop app on macOS or Linux is via our terminal installer:
curl -sL https://raw.githubusercontent.com/fabriziosalmi/mixi/main/install.sh | bashAlternatively, to build and run it locally:
git clone https://github.com/fabriziosalmi/mixi.git
cd mixi
npm install
npm run devOpen http://localhost:5173. Load audio files. Mix.
npm run build
npm run previewnpm run build:all
npm run dist # current OS
npm run dist:mac # macOS
npm run dist:win # Windows
npm run dist:linux # LinuxExtended analysis, file management, and MCP bridge for external agents.
cd api
pip install -r requirements.txt
python main.py --port 7779| Module | What It Does |
|---|---|
| Dual Decks | Independent transport, pitch/tempo, hot cues, loops, scratch emulation. 19 pluggable deck modes: Track, Groovebox, TurboKick, TurboBass + 16 community instruments (TurboFM, TurboSynth, TurboVox, and more via mixi-decks). |
| TurboKick Deck | Kick drum synthesizer + 16-step sequencer. THUMP macro, dual valves (tube + punch), filter + LFO, Berghain-style RUMBLE. |
| TurboBass Deck | Acid synth with 4-pole diode ladder filter (AudioWorklet, mismatched first pole, per-sample tanh saturation, 2x oversampling). Mathematically derived DSP: VT from pole signal geometry, k_max from Barkhausen criterion, resonance compensation, quadratic curve. Saw + variable duty-cycle pulse wave, sub-oscillator, analog drift, pre-filter drive/HP. Bipolar filter envelope, octave-based env mod, accent with resonance-controlled depth. TIE (legato), gate length, slide time, filter tracking (Devil Fish mod). Rat-style distortion, ducking spring reverb, chorus, BPM-synced delay. ACID macro, copy/paste, pattern mutate/shift, 32 factory patterns (4 banks), 16/32-step sequencer. Two-row knob UI. |
| 3-Band Isolator EQ | Parallel Linkwitz-Riley 24dB/oct crossover. Kill = gain 0, other bands unaffected. |
| Deck Effects | 10 built-in (7 in FX strip + 3 system): Filter (inline bipolar LP/HP), Delay (BPM-synced), Reverb (synthetic IR), Phaser (4-stage allpass), Flanger, Gate (beat-locked chop), Bitcrusher, Echo (dub delay with LP feedback), Tape Stop (LP darkening), Noise (white noise sweep). Parallel sends, gain-compensated. |
| Master DSP | Band-split distortion, gain-compensated parallel compression, DC blocker, brickwall limiter. Sub-bass mono sum. |
| Rust DSP Engine | Full signal chain in Wasm AudioWorklet. Per-deck EQ/FX/Fader + spectral sidechain compression + master chain. 10µs/block, 99.6% headroom. Zero-alloc hot path. Toggle in Settings. |
| AutoMixer | Stateless 20Hz-tick arbiter. Reads a Blackboard of deck states. Applies Ghost Mutations — visible, auditable corrections for phase drift, spectral clash, headroom recovery. 20 intents across 5 domains (safety, spectral, dynamics, rhythm, structure). |
| Groovebox Deck | 4-voice step sequencer (kick/snare/hat/perc) with drum synthesis on a decoupled bus. Own panning, mute, solo. Synced to master BPM. |
| BPM/Key Detection | Powered by open-bpm: 7-estimator architecture (IOI + Comb + AC + Spectral FFT + Hopf + Tempogram + Low-band AC), SuperFlux onset detection, metrical fusion for octave resolution. 68.8% Acc1 on GiantSteps, 8.5:1 vs librosa. Two-speed API (fast + full). Goertzel chromagram for key (Camelot). Pure Rust/Wasm — no browser pre-processing. |
| MIDI | WebMIDI API. Map any CC/note to any parameter. MIDI Clock Out/In (24 ppqn) for external gear sync. |
| MIXI Sync | Binary sync protocol (64-byte UDP packets, port 4303). PID phase lock, auto-discovery, master election, predictive VJ triggers. BroadcastChannel fallback for browser. |
| Beatmatching | Aerospace-grade PLL phase correction, harmonic sync, predictive phase, differential phase overlay, variable beatgrid, onset correlation, groove offset, drift compensation, audio clock reconciliation. |
| Waveform | Min-max decimation, drag-to-scrub, beatgrid editing (Shift+Click), BPM confidence display, overview viewport drag, energy shadow, zoom sync. Direct DOM writes, no React reconciliation. |
| Headphone Cue | Split-stereo or dual-output routing. Mix knob blends cue and master. |
| Recording | Crash-proof WAV recording (SPSC ring buffer → disk, 1MB fixed RAM). WebM fallback in browser. Orphan recovery on crash. |
| WebGPU VFX | 14-effect GPU shader: spectrum border, beat shockwave, particles, plasma, CRT, Tron floor, feedback loops. Ring texture spectrogram (64-frame history, 30 KB/s GPU upload). Canvas 2D fallback. ESC kill-switch. |
| Native Audio | Optional cpal output via N-API addon (Electron). CoreAudio/WASAPI/ALSA bypass. Zero-copy SharedArrayBuffer ring. |
| 17 Skins | Runtime-switchable. Pure CSS custom properties — zero JavaScript per skin. |
Acid, Aqua, Arcade Invaders, Blackfluo, Bloodmoon, Casino, Dune, E-Ink, Freetekno, Gold, Hologram, Industrial, Matrix, Nordic, Synthwave, Vaporwave, White.
Each skin is a directory containing skin.json (metadata) and skin.css (CSS custom properties). To create a new skin, copy any existing one and modify the variables. No TypeScript changes required.
Dedicated touch-optimized UI, code-split so desktop never downloads mobile code. Detects phones (minDim < 500 + touch) and loads a purpose-built layout.
- Portrait — Single-deck focus: hero BPM display, tall waveform, inline EQ/FX/PADS toolbar. Tap A/B to switch focus. Mini-strip shows the other deck's state. Crossfader pinned at bottom for thumb access.
- Landscape — Dual-deck mixing: both decks side-by-side with waveforms, pitch faders, nudge buttons, and a horizontal crossfader.
- Overlays — Slide-up glassmorphism panels (spring animation) for EQ, FX grid, performance pads, and headphone routing. Swipe down to dismiss.
- Haptics — Vibration feedback: tick on pad tap, snap on crossfader center detent, confirm on cue save, panic on shake reset.
- Shake-to-panic — Shake the phone to reset all EQ, FX, loops, and crossfader to defaults.
- Beat pulse — Deck card borders flash in sync with the BPM for visual rhythm feedback.
- PWA — Installable as a standalone app on iOS and Android. Safe area inset handling for notches.
src/
audio/ Core engine, DSP nodes, sample manager, BPM/key detection
dsp/ Wasm DSP bridge, SharedArrayBuffer param bus, worklet lifecycle
nodes/ DeckChannel (LR4 EQ), MasterBus, HeadphoneBus, DeckFx
recording/ Crash-proof WAV recording bridge
native/ Native audio output bridge (cpal/N-API)
gpu/ WebGPU VFX renderer, WGSL shaders, GPU detection
ai/ AutoMixEngine, Blackboard, Ghost Mutations, intents
decks/ Pluggable deck modes (TurboKick, TurboBass + 16 community decks)
sync/ MIXI Sync protocol (packet codec, PID phase lock, bridge)
groovebox/ Step sequencer engine, drum synthesis, UI
automixer/ AutoMixer panel, beat utilities
midi/ WebMIDI manager, controller mapping
components/ React UI — decks, mixer, browser, HUD, settings
mobile/ Touch-optimized mobile UI — portrait, landscape, overlays
store/ Zustand stores — mixer state, settings, MIDI, samples
hooks/ React hooks — sync bridge, keyboard shortcuts, drag, beatmatching
bridge/ MCP bridge for external agents
utils/ Logger, skin loader, watermark
types/ Shared TypeScript interfaces
mixi-core/ Rust DSP engine (Wasm) — EQ, FX, limiter, analysis
mixi-native/ Rust N-API addon — cpal audio output (Electron)
electron/ Electron main/preload, WAV header, native audio IPC
tests/ Unit tests (vitest) + E2E (Playwright)
Design constraints:
- React never touches AudioContext directly. A one-way bridge (
useMixiSync) subscribes to Zustand state changes and pushes them to the audio engine viasetTargetAtTime. - High-frequency visuals (VU meters, vectorscopes, waveforms) write to Canvas or DOM refs, bypassing React reconciliation entirely.
- The automixer is stateless by design. It reads a Blackboard snapshot every 50ms and emits deterministic corrections. No FSM, no accumulated state, no drift.
| Layer | Technology |
|---|---|
| UI | React 19, TypeScript (strict), vanilla CSS + CSS custom properties |
| State | Zustand 5 with transient selectors |
| Audio | Web Audio API — hand-wired graph, no wrappers |
| DSP | Rust/Wasm (mixi-core) — AudioWorklet, SharedArrayBuffer, zero-alloc |
| GPU | WebGPU (WGSL shaders), Canvas 2D fallback |
| Native I/O | cpal via N-API addon (Electron), CoreAudio/WASAPI/ALSA |
| Bundler | Vite 6 |
| Desktop | Electron 41 |
| Backend | FastAPI + MCP server (Python, optional) |
| Tests | Vitest (568), Playwright E2E (106), cargo test (198 Rust), BPM bench (164) — 1036 total |
| Docs | VitePress, 24 languages |
| Command | Purpose |
|---|---|
npm run dev |
Vite dev server + API sidecar + MCP server |
npm run dev:ui |
Vite dev server only |
npm run build |
TypeScript check + Vite production build |
npm run preview |
Serve production build locally |
npm run dev:api |
FastAPI sidecar on port 8000 |
npm run dev:mcp |
MCP bridge server |
npm run dev:electron |
Electron + Vite in dev mode |
npm run dist |
Package desktop app for current OS |
npm run docs:dev |
VitePress dev server |
npm run docs:build |
Build documentation site |
npm test |
Run unit tests (Vitest, 568 tests) |
npm run bench |
BPM detection + sync bench (164 tests) |
npm run test:e2e |
Playwright E2E tests (106 tests: smoke + mixer validation) |
npm run test:watch |
Watch mode for unit tests |
npm run test:coverage |
Test coverage report |
cd mixi-core && cargo test |
Rust DSP tests (198 tests) |
Contributions are welcome. Please sign the CLA on your first pull request — enforced automatically via GitHub Actions.
PolyForm Noncommercial License 1.0.0
Free for personal use, education, research, hobby projects, and non-commercial performance. The license explicitly permits underground gigs, academic work, and private experimentation.
Commercial use requires a separate license. Contact: fabrizio.salmi@gmail.com
- js303 by thedjinn — the original Web Audio TB-303 emulation that inspired the TurboBass deck. Awesome bass.
Built by Fabrizio Salmi