So what music exists in your fictional setting and does it encourage mood changes as our own can do? Or because music is known to affect mood, is it treated (and controlled) like a classified substance? How are orchestras made up? What musical instruments exist in your world? Is learning to play an instrument encouraged in schools?
What kind of songs exist in your fictional setting? Are there any contests (I'm thinking as I type that of Eurovision)? Do your characters, regardless of background, enjoy music or does one group say, for reasons of its own, ignore music altogether?
Music can be powerful and encourage relationships. Does anyone try to control/stop/abuse that?