Expo, Nr. 31

Expo is the penultimate in a series of works dating from the late 1960s which Stockhausen designated as "process" compositions. These works in effect separate the "form" from the "content" by presenting the performers with a series of transformation signs which are to be applied to material that may vary considerably from one performance to the next. In Expo and three companion works (Kurzwellen for six performers, Spiral for a soloist, and Pole for two), this material is to be drawn spontaneously during the performance from short-wave radio broadcasts (Kohl 1981, 192–93). The processes, indicated primarily by plus, minus, and equal signs, constitute the composition and, despite the unpredictability of the materials, these processes can be heard from one performance to another as being "the same" (Kohl 2010, 137).