Well, since literally anything (a sound, smell, object, etc.) can be a trigger, than it makes sense that one of your triggers for switching would be music. I don't have anyone to switch into, but depending on the music that's playing, my mood can entirely change. I have found that I can prolong certain moods by listening to certain types of music. Usually, it's movie soundtracks.
If a scene in a movie resonates with me, I will often go online and find the song that played during that scene, download it, and play just that song on repeat for who knows how long. Last time was after I saw the movie Breaking Dawn, and I downloaded the song that played at the end while Bella changed. That song was literally the only thing playing on my ipod for a solid week.

It had the ability to make me feel joyful, but it also had the ability to make me lay in bed and cry for a really long time
The type of music you like says a lot about your personality. So...if you other personalities in you it would make sense that they may like different music than you do. Music brings out emotion, and alters are often all
about emotion, or so I've heard

So if you think it will help them come out (and you want them out) I say go for it!