I almost always turn music off in RPG game mainly because I don't like the way music always changes so abruptly in response to events like combat or area change - I just always find it more irritating than atmospheric. My enjoyment is typically greater without music. Now - ambient sound is a different thing altogether - that always enhances if done well.
That saying a good theme such as the one illustrated here does help atmosphere but I wonder if it would be possible to have a setting that turns off looping so a player can hear such tunes upon entry to an area to create the mood but then have them fade out after a single play and rely on ambient noises to maintain that mood?