I found this music at https://modarchive.org/ https://www.youtube.com/watch?v=sBPQd42yNo0
Thanks Iskander! I also realized that if you download the game, the music is included as regular old sound files, ready to play :)
Please note that itch io contains very outdated. :) I have plans to update it, but it takes time to optimize a bigger game for a web export.
