Thank you for your appreciation Maltosier! We're really happy to hear that you enjoy our game.
If you wish to volunteer make sure to join us on Discord and report any bug or typo in the bug-report channel, WistieCutie, the developer will have the pleasure to hear about that and fix it.
As for the soundtracks, some of them are free to use soundtracks, since we started the game when there was no official music composer, it was complicated to get some original soundwork. However with time, we've had some wonderful people contribute to this game and our community manager, Mikan Tsumikiwi, gathered all the original soundtracks on a band camp album which are also on YouTube.
As far as I can tell, one of the bonus of the game is a music box that offers you the possibility to listen to the original soundtracks of the game.
Cheers ✨ :).