I tried looking through the game's music files. I mostly didn't find anything interesting, but I did find these two tracks that appear to be unused.
https://www.youtube.com/watch?v=7UbLPMcwg8k (A track featuring the melody from the Acolytes' theme. It sort of sounds like a dungeon theme, strangely.)
https://www.youtube.com/watch?v=qBTQGXGCzII (This appears to be a more dramatic version of the "level up" jingle. I'm not sure what it was meant for)
(Side note: there are also like 6 different versions of the Sleeper Island map theme in the files, and the "corrupted" version of the resting jingle that plays in the illusion sequence is copied several times as well, for some reason.)
