Usually the default game music, but I just got Asylum by disturbed so I've been listening to it while traveling/dungeon crawling. Sometimes I listen to Slipknot, or Dethklok though. Really what ever I'm in the mood for.

FreeDog, aaoooooooooooh!

This. I don't want the game alerting me via a musical soundtrack. That would totally blow immersion.

my game music is off most of the time, in both Oblivion and Skyrim. The only time I turn it on is if my character is in a rich person's house, or in the Blue Palace...somewhere opulent. And even then, I'll only put music on its very lowest setting. I figure they could have some musicians hidden off in a room somewhere, or even a magical device that plays tunes or something like that.

Instead of music, I usually open up the glass door that leads into my room. There's forest back there, with birds singing, wind blowing, rain falling at times. In the summer there's also crickets and katydids making lots of noise at night. The way it works, sometimes it's hard to know where the in-game birds and wind and insects stop, and real-life noises behind my home begin.
.

This. I don't want the game alerting me via a musical soundtrack. That would totally blow immersion.

my game music is off most of the time, in both Oblivion and Skyrim. The only time I turn it on is if my character is in a rich person's house, or in the Blue Palace...somewhere opulent. And even then, I'll only put music on its very lowest setting. I figure they could have some musicians hidden off in a room somewhere, or even a magical device that plays tunes or something like that.

Instead of music, I usually open up the glass door that leads into my room. There's forest back there, with birds singing, wind blowing, rain falling at times. In the summer there's also crickets and katydids making lots of noise at night. The way it works, sometimes it's hard to know where the in-game birds and wind and insects stop, and real-life noises behind my home begin.
.