Opus Score Editor

A music score editor with its own engraving engine, and WebAudioFont for playback.

Work in progress — this is an experiment under development.

Live demo

Features

• Note entry by clicking the staff
• Chords, ties, tuplets, and articulations
• Time signatures, including changes mid-score and pickup bars
• Clefs (treble, bass, alto, tenor), including mid-measure changes
• Automatic rests, beaming, and stem direction
• Playback
• Undo and redo
• Save and load as JSON

Tech Stack

• No UI framework — plain TypeScript and the DOM (Vue was removed; see docs/history/remove-vue-plan.md)
• Our own engraving engine — notation rendering (first built on VexFlow 5, since removed; its MIT-licensed ports are credited in NOTICE)
• WebAudioFont — sampled General-MIDI audio playback (samples fetched from CDN at play time)
• Tailwind CSS — styling
• Vite — build
• Vitest and Playwright — testing

Running it

Requires Node.js 20.14.0 or higher.

npm install
npm run dev        # start the dev server
npm run build      # production build
npm run test       # unit tests
npm run test:e2e   # end-to-end tests

License

Copyright (C) 2026 Kiko Faxas

Licensed under the GNU Affero General Public License v3.0 or later. See LICENSE.