I think depending on the layer in which an event is taking place (and the keeper is viewing) should change which style of music is played.
Something like a dark classical orchestra on the surface (battle music) or a light "happy" orchestra when peaceful.
Dark gothic ochestra in the dungeon level (battle) and some sort of "industral" for peace time (like DK1's industral style).
I'm not sure on the deeper dungeons, it could mimic layer 2's music I suppose.
This is what I was listening to when I got the idea:
http://www.newgrounds.com/audio/listen/83021
It starts a bit weird, so give it some time.
http://www.newgrounds.com/audio/listen/264623
Peaceful time on the surface? Not too keen on this...
I have a feeling the music for peace might come on too strong. Or if the player is switching a lot the music might get a bit confusing, could be combatted with trying the same rhythm but in two styles, and fading the two together.