It's not music, it's sound (gasp). It looks like BaiBai forgot to create a sound channel, or maybe they misspelled it. I don't remember such an error in my play, but it might have appeared in later updates. You can try creating this channel yourself as a quick fix. Just create a file in the "game" folder called sound_fix.rpy (or use another name but keep the .rpy extension) with the following content:
Python:
init pyton:
renpy.music.register_channel("hsfx1", "sfx")
Just a heads-up: It's important to make sure there are no tab characters in the code (in the indent before renpy...). You need to use spaces instead. Otherwise, Ren'Py will crash with an error on startup.
I haven't had a chance to test the code yet, so let me know if you run into any issues.
By the way, it would be nice if you could inform BaiBai about the bug in Discord, I'm not sure if he reads the forum here.