Try it: in ZQuest, try to open something like "End of Time" or "Link's New Technicolor World". When it tries to read the music, it will fail.
Can't open older quests!
This appears to be a Mac-only problem. I'll try to look into it, though I don't have a Mac myself.
Until this problem is fixed, please be aware the Mac build is probably saving corrupted quests.
I've committed a potential fix; if that doesn't solve your problem you'll need to determine exactly where MIDI loading is failing for me.
Thanks!