Metronome

A browser-based metronome with DSP written in Rust and compiled to WebAssembly.

Tech

• Rust — click synthesizer and beat engine (metronome-core). Zero-allocation, no_std-compatible audio code: sine burst with exponential decay envelope, phase accumulator-based beat scheduling.
• WASM — Rust compiled to wasm32-unknown-unknown via a C ABI. The AudioWorklet holds an opaque pointer to the engine and calls into WASM once per 128-sample block (the Web Audio fixed block size), keeping latency low and click timing sample-accurate.
• Web Audio API / AudioWorklet — DSP runs on the dedicated audio thread. The main thread only sends parameter messages (BPM, beats/bar, gain, accent).
• Vite — bundles the frontend.
• nginx — serves the static build with the Cross-Origin-Opener-Policy / Cross-Origin-Embedder-Policy headers required by SharedArrayBuffer and AudioWorklet cross-origin isolation.

Build & run locally

Prerequisites: Docker

docker build -t metronome .
docker run --rm -p 8080:8080 metronome

Open http://localhost:8080.

Run from GitHub Container Registry

docker pull ghcr.io/mfisher31/metronome:latest
docker run --rm -p 8080:8080 ghcr.io/mfisher31/metronome:latest

Open http://localhost:8080.

Development (without Docker)

Prerequisites: Rust, wasm32-unknown-unknown target, Node 20+

rustup target add wasm32-unknown-unknown
npm install
npm run dev

License

MIT — see LICENSE.