Over time mimimalist composers adopted more and more chromatic material for repetition, for example Philip Glass' Symphony No. 2, and the operas of John Adams. There was also an increasing movement to incorporate found sounds, tape, electric or electronic sources of music. Minimalism in classical music often cross fertilizes with popular experimental music, such as the work of Brian Eno and Mike Oldfield, as well as electronica and house, where DJs layer different recordings on top of each other without regard for their source
