You can edit the source code, in data folder search the bgMusic.ogg and replace it with other you like or with an empty song for no sounds.Would you add a settings option to disable music?
Or edit application.cpp or main.cpp (I don't remember) and there is a line at the beginning that says the music file and then there is a number in brackets (normally it is 50) you can write 0
Or @Maschell coul do it, but he is busy with the language setting
Or the easiest way, turn off GamePad volume xD
Bye!