I may just post this in the bug report thread and see if anyone addresses it.
Viewing post in Title Screen music change
I know which event you're referring to, and I can't for the life of me remember what I did to make the music go back to normal after triggering the music change. I just replayed the event in question because I wanted to see if I could replicated whatever I did to make it go back to normal, but I can't seem to remember what I did, or, for that matter, if I actually DID do anything or if it's just random and I got extremely lucky one day.