Music obviously adds a lot to the experience; I just was visiting Steamfont Mountains(?) on a quest for the first time and damn if that isn't a jaunty little theme for the zone, I liked it so well that as I sped toward the entrance to Ak'Anon a sudden burst of movement in the song caused me to divert off and back into the surrounding area for a couple of more encounters. What are some of your favorite bits of music from the game? I can't imagine all the different zone music I've yet to hear.
Off the top of my head I've really enjoyed
Steamfont Mountains
Freeport
Natimbi
Dranik's Scar