music that envelops the listener...
Ambient music is a musical genre that incorporates elements of a number of different styles - including jazz, electronic music, new age, rock and roll, modern classical music, traditional, world, and noise.
It is sometimes characterized as possessing a sense of resonant sonic space, and of being designed to function equally effectively for both passive (background music) and active listening.
"Ambient Music must be able to accommodate many levels of listening attention without enforcing one in particular; it must be as ignorable as it is interesting." - Brian Eno (Music for Airports liner notes, September 1978)
Reference Wikipedia: http://en.wikipedia.org/wiki/Ambient_music