You can add up to 10 music file. If you add more, the extras just wont be played.

Name of the files must be:

BagMusic01.wav
BagMusic02.wav
BagMusic03.wav
BagMusic04.wav
BagMusic05.wav
BagMusic06.wav
BagMusic07.wav
BagMusic08.wav
BagMusic09.wav
BagMusic10.wav


They can be either wav or xwm