Split sampled piano sounds
FluidR3 GM SoundFont by Frank Wen, with contributions credited by the Fluid SoundFont project.
Electric Piano 1, rendered to MP3 by Benjamin Gleitzman (midi-js-soundfonts).
Source: https://github.com/gleitz/midi-js-soundfonts/tree/gh-pages/FluidR3_GM
License: Creative Commons Attribution 3.0 US
https://creativecommons.org/licenses/by/3.0/us/
Changes: extracted MP3 samples into pitch-indexed JSON; playback gain, filtering and release envelopes applied at runtime. No affiliation or endorsement.
These sample assets are separately licensed; the license does not apply to Split's proprietary application code or models.

Acoustic grand: Salamander Grand Piano V3 by Alexander Holm.
Source: https://github.com/sfzinstruments/SalamanderGrandPiano
MP3 velocity-6 sample distribution: @audio-samples/piano-mp3-velocity6 1.0.5
https://www.npmjs.com/package/@audio-samples/piano-mp3-velocity6
License: Creative Commons Attribution 3.0
https://creativecommons.org/licenses/by/3.0/
Changes: repackaged MP3 samples as pitch-indexed JSON; nearby notes transposed at playback, velocity gain, filtering and release applied.