It's loud as fuck in my headset
Only thing I've found that mutes it is if I start up MLG and then back out.
But even then sometimes it starts playing.

Anyone know?

music.

bad

but really try xbox settings (the middle button i believe there is a way to turn off music.)

start the countdown
when it gets to one second
delay it and music is gone

You don't have to go to one second, just hit A B and it's done.

That's what I've been doing, but recently I've noticed if I sit there long enough talking to someone sometimes it starts back up
Really annoying.
It's only happened a few times though, maybe it was a fluke.

press xbox button on controller... thats all i know. :/

start matchmaking up and backout or turn volume down and back up when in game

Go to your custom games and press A and X and the music goes away. You don't need to wait for the count down or anything. You can do the same in matchmaking lobby.