Boss music

I've been wanting to try out boss themes for some of my mods for a bit, haven't gotten to it yet, but I have an idea of how it might work.
Of course, you'll need to add a sound (probably set as music) to the mod.

Then have a procedure that runs every player tick, and checks if theres any of a certain mob/mobs that are within a certain block radius. And have it play when they are.
Though, this would also mean that the music would start and stop suddenly.

So another way that may work better would be having the boss entities always play the music, Not sure how exactly, but it should be set as some kind of mob sound so that the further away, the quieter it is.