to put music in you need to put the music files into the music folder of your mod. Then change the music file, preferably with module system (module_music), you need to put the name of the music file in the part where you want that music to play.
I have a question for you, you have written on mbrepository that u have commoners,semi-professionals and elites. Did you do this by having different troops being trained in villages or castles? if so how did you do this?