Okay, I more or less figured out a solution. I'm not 100% sure which of these steps solved the issue, but it was some combination of the following:
- I started over from a fresh copy of my project (it always pays to test stuff in a backup copy!) and installed the Extended Music Room properly with only a single instance in the folder to begin with.
- This time, I didn't copy the content of the music_room.rpy over to screens.rpy, and instead just edited music_room.rpy directly itself (I think this was most likely the main issue, user error on my part. The tracks I added into music_room.rpy appeared properly at this point.)
- I also noticed that specifying the path name for the audio files while leaving the angle brackets in place (ex: path="<audio/track1.ogg>",) Ren'Py threw an error when I tried to play Track 1. But when I removed the angled brackets and just listed it as path="audio/track1.ogg", everything worked correctly.
Thanks for your suggestions! They did help me figure out what I was doing wrong. If I bump into any more issues I'll post back, but I think it's looking good now!