I enjoy the ambient backgroud music (all instrumental). Mouse World X and Mouse World X2 are great. Each area loop lasts about an hour. My very favorite is the Wilderness Lodge music, with a heavy dose of Aaron Copeland, one of the great American composers.
Here are their playlists:
MOUSE WORLD X
Adventureland Music Loop
Canada Area Music Loop
Crystal Palace Music Loop
The Land - Area Music Loop
The Land - Exterior Loop
WDW Main Entrance
Wilderness Lodge Loop
Wonders of Life Area Music Loop
Frontierland Area Music Loop
Land - Area Music Loop 2
MOUSE WORLD X2
Innoventions Plaza
Living Seas Music Loop
Main Street USA Area Music Loop
Pizzafari Area Music Loop
Sci Fi Dine In Theater Movie Loop
Sunset Blvd Area Music
Tree of Life Garden Area Music
International Gateway Area Music Loop