4-track tape also led to a related development, quadraphonic sound, in which each of the four tracks was used to simulate a complete 360-degree surround sound. A number of albums including Pink Floyd's "The Dark Side of the Moon" and Mike Oldfield's "Tubular Bells" were released both in stereo and quadrophonic format in the 1970s, but 'quad' failed to gain wide commercial acceptance. Although not a commercial success at the time, it was the direct precursor of the surround sound technology that has become standard in many modern home theater systems.