“Persian Surgery Dervishes is a recording of two live solo electric organ concerts, the first held in Los Angeles on 18 April 1971 and the second in Paris on 24 May 1972, by avant-garde minimalist composer Terry Riley, following his A Rainbow in Curved Air and In C. The two very different performances of the same composition “Persian Surgery Dervishes” are meant to show the importance of improvisation in Riley’s music. Riley plays a modified Yamaha electric organ tuned in just intonation. The original double-record version was released by the French label Shandar, then republished, first by Mantra Records, then by Dunya Records. There existed also a single-record version, also on Shandar, containing just the Paris concert, which had been sponsored by the label itself” – Wikipedia.
