Yep, probably many of you had this problem: the music was not heard.
I related this problem with the Friend List BECAUSE my list was glitched before, if I wanted to get friend requests these would not display in my Friend List and the only way to accept requests was friending a penguin that sent me a request BUT someday I just wanted to clean a bit my friend list unfriending some penguins, idk I think I unfriended 10 of them (my list now has 332). Today I logged on and my friend list had 6 requests, it was the first time in months that I saw friend requests there, I went to play Card Jitsu and THE MUSIC WAS THERE!!! I also went to play other games like Ice Fishing, Bean Counters, Thin Ice and the music was back!
If you guys have this problem with the music, try cleaning a bit your Friend List, it might help :)