Are you on HEN? I just tested it on AC Brotherhood (Rebug 4.86.1 LITE) and it worked as expected (you press PS, go to Music column and play a music file).
However, it may freeze the console when you try to return to XMB. Probably some libraries stay loaded.
Nah, i'm back on CFW.
I tried on JB format game, does it matter?
Edit: Just tried it on a pkg game and same thing
I'm on Rebug 4.84.1, when exiting the game the console will beep and restart as expected, but it won't allow the music playback.