The instrument sounds in this product are recordings of real instruments used under the licenses below. No model was trained on any of them, they are played back as instruments, the way any sampler or DAW plays a sample.
harpsichord, marimba, vibraphone, glockenspiel, concert harp, and the full acoustic drum kit, bass drum, snares, hi-hats, toms, cymbals, claps tambourine, cowbell, shaker, claves, woodblock, conga, bongo, cajón.
Attribution is not required by CC0. It is given anyway, because the work is good and the people who did it should be named.
Every sample was truncated, level-trimmed and transcoded to Opus for the web; web/audio/manifest.json records the license, source and retrieval date for each instrument, and tools/fetch_instruments.py is the exact process used.
The two instruments below are CC-BY, not CC0. They are free to use commercially, permanently, on one condition: they must be credited. That condition does not expire and is not satisfied by intending to.
Do not remove these lines. tools/verify_credits.py reads the required credit out of web/audio/manifest.json and fails if it is not found in this file. Run it before any release.
| Instrument | Required credit | |
|---|---|---|
| Salamander grand | Salamander Grand Piano V3 by Alexander Holm, CC BY 3.0 | source |
| Studio kit | MuldjordKit by Lars Muldjord, CC BY 4.0 | source |
They were taken on despite the condition because they are audibly better than anything CC0 that was found: the Salamander is a Yamaha C5 captured at sixteen velocity layers, and MuldjordKit is a real multi-microphone kit with alternate takes on every drum. Both are the default choice for the styles that want an acoustic sound.
The electric and synth basses, the guitars, the FM electric pianos, the pads and the drum machine come from FreePats, which publishes each sound bank in its own repository under a CC0 1.0 public domain dedication. The license was checked against the LICENSE file in each repository rather than against a web page, CC-BY 4.0's own boilerplate contains the phrase "public domain dedication", so a page-level or substring check is not evidence.
These are the instruments that made the difference: before them every sampled instrument in the product was orchestral, there was no bass sample of any kind, and every style came out sounding classical.
| Instrument | Source repository | License |
|---|---|---|
| Bass lead | synth-bass-lead | CC0 1.0 |
| Bowed pad | synth-pad-bowed | CC0 1.0 |
| Choir pad | synth-pad-choir | CC0 1.0 |
| Drum machine | synthesizer-percussion | CC0 1.0 |
| Electric bass | electric-bass-YR | CC0 1.0 |
| Electric guitar | electric-guitar-FSBS-clean | CC0 1.0 |
| Electric piano | fm-piano2 | CC0 1.0 |
| FM piano | fm-piano1 | CC0 1.0 |
| Felt piano | old-piano-FB | CC0 1.0 |
| Jazz guitar | electric-guitar-FSBS-jazz | CC0 1.0 |
| Nylon guitar | spanish-classical-guitar | CC0 1.0 |
| Sub bass | lately-bass | CC0 1.0 |
| Sweep pad | sweep-pad | CC0 1.0 |
| Synth bass | synth-bass-2 | CC0 1.0 |
Two libraries were evaluated and not used, both usable commercially but neither public domain: MuldjordKit (CC-BY 4.0, an excellent multi-velocity acoustic kit) and the Salamander Grand Piano (CC-BY 3.0). They are listed in tools/fetch_freepats.py so nobody re-evaluates them from scratch. ColomboADK was rejected as GPL.
tools/fetch_freepats.py is the exact process used, and tools/normalize_levels.py records how each instrument's level was measured.
Served from this domain rather than from Google Fonts, so that loading a page contacts nobody else. All three are under the SIL Open Font License 1.1 which permits bundling and redistribution inside a larger work and requires that the notice travel with the files, it is at web/fonts/OFL-NOTICE.txt.
| Typeface | Designer | License |
|---|---|---|
| Archivo | Omnibus-Type | OFL 1.1 |
| Instrument Sans | Instrument | OFL 1.1 |
| IBM Plex Mono | IBM | OFL 1.1 |
tools/fetch_fonts.py is the exact process used to retrieve them.
No sample library requiring attribution or a paid license is currently shipped. Everything above is CC0. ColomboADK was rejected as GPL: a sample library under the GPL raises questions about the work it ships inside, and that argument is not worth having.
The Salamander Grand Piano and MuldjordKit were once listed here as evaluated and rejected for being CC-BY rather than CC0. That decision was reversed on 2026-09-01, they are now shipped, and credited above under the section that a build check enforces.