Compás DJ

The DJ/performance app in the Compás family — a shared Rust audio core, focused products on top. A Compás Studio DAW is planned.

A cross-platform, real-time professional DJ application. Rust audio core + TypeScript UI in a Tauri 2 shell. Windows is the primary target; macOS is first-class; Linux is best-effort.

Scope & honesty. Compás DJ does true DSP mixing on local DRM-free files — that is the real DJ engine, and the focus of the app today. Optional streaming-service control decks are on the roadmap; since services expose playback control, not decoded audio, any such deck would be control-only by design and the UI would disable the DSP it can't perform. See ARCHITECTURE.md §1.

Status: active development. The local DJ engine is functionally complete and self-reported working in the app; work now is on a richer performance/library layer and a signed public release, plus planning Compás Studio (the DAW). See ROADMAP.md for the full plan, STATUS.md for the live resume point, and docs/COMPAS-STUDIO-PLAN.md for the DAW roadmap.

What it does today

• 4 decks, in-RAM decode with a cubic-Hermite play-head (instant seek/varispeed/scratch/loops).
• Mixer: equal-power crossfader (per-deck assign), per-deck gain, full-kill 3-band EQ, HPF/LPF filter.
• Analysis: BPM + beatgrid + musical key (Camelot), scrolling zoom + overview waveforms, manual grid nudge.
• Tempo: varispeed + fine trim, continuous tempo+phase SYNC (audio-thread PLL), key-lock (in-house WSOLA).
• Performance: beat loops, hot cues, jog-wheel scratch, beat-jump, loop-roll w/ true slip, quantize.
• FX rack (per-deck inserts): echo/delay, reverb, beat-synced flanger, bitcrusher.
• Sampler: 8 performance pads (one-shots + per-pad loops) on the master bus.
• MIDI: controller input + per-target MIDI-learn mapping; one-click Akai MPK Mini MK3 profile.
• Headphone/cue (PFL) monitoring on a 2nd output, master WAV recording, auto-mix transitions.
• Library: local SQLite track DB (cues/loops/grid/gain/play-history persisted), search, A/B/C/D load.
• Release: in-app auto-update + a manual "check for updates" version chip.

Coming next: playlists/crates depth, harmonic-mixing assist, an expanded FX/controller-scripting layer, and the Compás Studio DAW on the shared core. See ROADMAP.md.

Note: AI stem separation (Demucs/htdemucs) was removed — the upstream project is archived and we're not shipping AI for now.

Download

Prebuilt installers for Windows, macOS, and Linux are published on the Releases page (built and attached by CI on each v* tag). The project landing page in website/ links directly to the latest per-OS installer. The app then keeps itself current via the built-in updater.

Beta builds aren't code-signed yet, so your OS will warn on first launch (the app is safe — it's Gatekeeper / SmartScreen blocking an unsigned download):

• Windows: SmartScreen → More info → Run anyway.
• macOS: if you see "Compás DJ.app is damaged and can't be opened" (common on Apple Silicon), drag it to Applications, then run xattr -cr "/Applications/Compás DJ.app" in Terminal and open it. Signed/notarized macOS + Windows builds are pending a paid Developer ID / code-signing cert.

The performance UI (Traktor-inspired dark theme): dual decks with per-deck color identity, center mixer (gain / 3-band EQ / filter / FX), stacked band-colored waveform lanes, library browser, and a live engine status bar. Brand mark = the "Needle & Rose" — a compass needle (the tonearm) inside a beat-ticked ring (compás = beat/measure).

Layout

crates/compas-core      domain types (TrackMetadata, SourceCapabilities, errors)
crates/compas-dsp       real-time-safe DSP + offline BPM/key analysis
crates/compas-audio     cpal engine, lock-free rings, mixer
crates/compas-sources   AudioSource abstraction: local-file decode + streaming control
src-tauri               Tauri 2 app (commands, engine thread)
frontend                React + Vite + TypeScript UI
website                 static landing page (downloads + repo link; deploy to Pages/Netlify)

Contributing & orientation: see CONTRIBUTING.md and AGENTS.md. Changes are tracked in CHANGELOG.md. CI (fmt + clippy + tests + frontend build + audit) runs on every push/PR.

Prerequisites

• Rust (stable ≥ 1.82) — https://rustup.rs
• Node.js ≥ 18 and npm
• Windows: WebView2 runtime (preinstalled on Windows 11) and the MSVC build tools (Visual Studio C++ workload).
• macOS: Xcode Command Line Tools (xcode-select --install).
• Tauri CLI: cargo install tauri-cli --version "^2" (or use the copy installed under frontend/node_modules — see below).

Build & run the engine (no GUI, fast)

The four engine crates build/test without WebView2 or a frontend build:

cargo check            # checks the engine crates (workspace default-members)
cargo test             # runs DSP/source unit tests
cargo clippy           # lint

Run the full app (desktop)

Compás DJ lives in apps/compas-dj/ (src-tauri/ + frontend/). Run the Tauri CLI from that product directory so it finds its src-tauri/ sibling:

# 1) install frontend deps (once)
cd apps/compas-dj/frontend && npm install && cd ../../..

# 2) dev mode (hot-reload UI + native rebuilds) — run from apps/compas-dj/
cd apps/compas-dj
frontend/node_modules/.bin/tauri dev          # macOS/Linux
frontend\node_modules\.bin\tauri.cmd dev      # Windows
#   ...or, with a global CLI: cargo tauri dev

tauri dev runs the Vite dev server (http://localhost:5173) and the native shell together.

Build a release bundle

cd apps/compas-dj && cargo tauri build   # installers under target/release/bundle/

App icons are generated from the "Needle & Rose" brand mark via npm run icons (in apps/compas-dj/frontend/, requires sharp), which rasterizes the SVG to apps/compas-dj/src-tauri/icons/*.

Notes for contributors

• Real-time discipline: nothing in the audio callback may allocate, lock, block, log, or panic. Functions safe to call there carry an RT-SAFE doc-comment; respect it. See ARCHITECTURE.md §8.
• Error handling: Result-based; no unwrap()/expect() in non-test code.
• Cross-platform from commit one: gate any platform-specific code and document it.
• Keep ARCHITECTURE.md and ROADMAP.md updated alongside code changes.

See CONTRIBUTING.md for the full workflow and CODE_OF_CONDUCT.md for community expectations. Good first issues: widening loops/cue modes, library crates/playlists, and FX additions — see ROADMAP.md.

License

compas is open-source under the MIT License — permissive: use, modify, and redistribute, including commercially, with attribution. The engine implements time-stretch/key-lock and beat/key detection in-house (no copyleft DSP dependency); the optional FFmpeg decode fallback is dynamically linked and documented. See ROADMAP.md for the full dependency-licensing table.

Acknowledgements

compas is an independent project. Thanks to the Rust audio ecosystem it builds on — cpal, symphonia, rubato, rtrb, rustfft, and tauri — and to the broader DJ-software community whose decades of established UX conventions informed the feature set.