the besta fast way is to save a registration that has styles + mp3 or wav. you can start play mp3 or wav and then start the styles, together too, you can across from mp3 to style using the volume, of course only the problem is sync. but if you want to us mp3 as intro that don't have the drum or tempo is ok
for effect. another way is to assign mp3 to key. is only important you press the key at tempo during play styles, then they are sync, but I don't know if registration save or recol the key mode (don't remember the "name" but is the keys where is program, voice list, ram then "key..." this is.