Acoustic guitar samples: tonejs-instruments by Nicholas Brosowsky.
Source: https://github.com/nbrosowsky/tonejs-instruments/tree/622c2f1c32c8cfce4158ddc3eb26e518ddef37e5/samples/guitar-acoustic
Original recordings: University of Iowa Electronic Music Studios (per library source notes).
Licence: Creative Commons Attribution 3.0 Unported
https://creativecommons.org/licenses/by/3.0/
Six MP3 samples redistributed unchanged. Playback volume is reduced in Levels Flow.