Credits
Echo is built on open source. These are the projects and assets it ships with, and the terms they are used under.
Notation and audio engine
- alphaTab
- Renders every score in the app and drives its SoundFont synthesis. Copyright © Daniel Kuschny and contributors, under the Mozilla Public License 2.0. Used unmodified.
Sound
- GeneralUser GS
- The General-MIDI SoundFont everything you hear is played through. Version 2.0.3, copyright © 1997–2025 S. Christian Collins, distributed under the author’s own permissive licence, which allows use in private and commercial music creation. Echo serves its own copy rather than linking to the author’s downloads, as that licence asks.
- SONiVOX GM
- The compact fallback bank, from the Android Open Source Project, under the Apache License 2.0.
- tonejs-instruments
- Acoustic guitar note samples by Nicholas Brosowsky, under CC BY 3.0. These backed an earlier sampler and are no longer played, but are still distributed with the app.
Typeface
- Bravura
- The SMuFL music font scores are drawn with. Copyright © Steinberg Media Technologies GmbH, under the SIL Open Font License 1.1.
Scheduling
- ts-fsrs
- The Free Spaced Repetition Scheduler, by the Open Spaced Repetition project, under the MIT License. It decides when every card comes back.
Platform and interface
The rest of the stack, all under permissive licences:
- React and Next.js — MIT
- Tauri — MIT or Apache 2.0, for the desktop app
- Supabase client libraries — MIT
- Radix Themes — MIT
- Lucide icons — ISC
- Vite and Zustand — MIT
If something here is attributed wrongly or missing, please tell us and it will be corrected.