This is really easy but it's mainly for people that dont know how to do it,and yea I know alot of you know how to do this but yea... :/
(Or you can disable in game)
1.Computer>C:>ijji>English>AVA>avaGame>Content>Mus ic
2.If you'r still at the "Music" folder drag the file either to your desktop or somewere else you want.
3.You know have no lobby music and other music that would be playing.