Ambient

Ambient music focuses on creating a mood or atmosphere through synthesizers and timbral qualities. It often lacks the presence of any net composition, beat, or structured melody. Due to its relatively open style, ambient music often takes influences from many other genres, ranging from house, dub, industrial and new age, amongst several others. Since it is a relatively ambiguous term, ambient has no distinct characteristics, and its style can vary a great deal. In essence, it is a term to describe any form of electronic music which puts an emphasis on tone and atmosphere over traditional musical structure or rhythm. Ambient music is often highly conceptual and experimental in style, while it is said to evoke an "atmospheric", "visual" or "unobtrusive" quality.

Associated Sub-Genres: Ambient Dub, Ambient Industrial, Ambient House, Dark Ambient, Drone Music, Illbient, Isolationism, Ambient Techno, Lowercase

Source: http://en.wikipedia.org/wiki/Ambient_music