Ambient music is a musical genre that is generally identifiable as being broadly atmospheric and environmental in nature. Ambient music evolved from early 20th century forms of semi-audible music, from the impressionism of Erik Satie, through "musique concrete" and the minimalism of Terry Riley and Philip Glass, and Brian Eno's deliberate sub-audible approach. Later developments found the dreamy non-linear elements of ambient music applied to some forms of rhythmic music presented in chill-out rooms at raves and other dance events, but always with the primary feature that the music is intended to drift in and out of the listener's awareness while creating its effect on the listener's consciousness.