Chord Progression Player

Progression is a backing-track tool for musicians. Enter a chord progression, set your key and tempo, and loop it while you practice scales, solos, or chord shapes.

App: https://dougflip.github.io/progression
Docs: https://dougflip.github.io/progression/docs.html

Local Development

# switch to proper node
nvm use

# install deps
npm i

# run the dev server
npm run dev

# run static analysis checks against the code
npm run check

# format the code
npm run format

Tests

Unit tests cover music theory logic and run via Vitest:

npm test

E2E snapshot tests run in Docker using Playwright (Chrome, desktop + mobile viewports). Snapshots are always generated inside the container for consistent rendering across environments and are committed to e2e/tests/snapshots/.

# run e2e tests
npm run e2e

# regenerate snapshots after an intentional UI change
npm run e2e:update-snapshots

Stack

HTML + CSS + JS + Tone.js