I think it would be best, whenever the MNC DLC comes out, that the music from the main menu slowly fades out when you enter the party lobby, i understand a lot of people might like the music but it gets a little repetitious while waiting for people to join
Current workaround: Start MNC, bring up the guide and go to select music (right 1, down 6). Pick any song to play (you need to load a song on your hd or have a network library first) then pause it. Now all the sound effects are there, but the intro and outro music won't play anymore. If you do it right after starting MNC you can keep the intro music from playing at all. My vote is replace the theme music with this: Perfect MNC music also: signed +1 and turtle beaches +2
Oh yeah! I totally forgot about that music trick. Also wow! It's been awhile since I heard about/been to Grooveshark.