Board Thread:M.U.G.E.N Help/@comment-26865490-20180926191144/@comment-3495717-20180927185945

If you simply want to change the music, find it in the character's sound file and replace it with the music of your choice in .wav format. If you want to add music to a character that lacks it, then it's a case of adding that music to the character's .snd file and triggering a PlaySnd for it, while also triggering an AssertSpecial with the nomusic flag to stop the stage music from playing; both will need to be placed in a dedicated Helper so they can persist through Pauses and SuperPauses.