If you have already gotten and answered this question, just leave this post be. But will every boss get a signature song? You could rename some songs like the boss (X) into the name of a boss. An idea I have is that some bosses will have some type of mixed song or combo if you spawn them all. I do only see one or two SENSIBLE combos though, the mech bosses and Plantera & Golem. So maybe it is up for debate.