I've put 3 wav files as asked into the data/sound folder and all of them have come up as errors and crashed the game. I hope this can be fixed, as I really enjoy the game.

Unfortunately the music player the SDK gives me is current;y broken: https://devforum.play.date/t/im-been-having-a-lot-of-trouble-with-the-fileplayer...

The devs hope it'll be fixed soon. Until then, WAVs won't work. MP3's will work, but I can't detect when it stops

When it gets fixed, I will likely have to convert some common/open tracks to PDA using their compiler and host them on a web page :(