One of La Monte Young’s disciples, Terry Riley became the guru of minimalist repetition with the pulse-based ensemble work In C, that centered on the iteration of simple patterns, and explored the psychedelic connection with the solo electronic improvisation Rainbow in Curved Air, that employed tape loop delays. These works clearly introduced repetition as a main compositional technique in western music, with Rainbow In Curved Air or without In C melody. This conceptual revolution mirrored the sociopolitical revolution of the time, when communal and improvised concerts prevailed over the formal presentation of classical music. The spiritual fervor of his Persian Surgery Dervishes marked the end of the hippy-inspired era. Riley would turn to more conventional formats, but still retain the titanic urge of his minimalist years, particularly in the monumental quartets Cadenza On The Night Plain and Salome Dances For Peace, and in the Requiem For Adam.