sentences:  He is regarded as one of the central figures of the Cologne School, active since the mid-1970s .Maiguashca worked closely with Stockhausen in the Electronic Music Studio of the Westdeutscher Rundfunk in Cologne from 1968 to 1972, and joined Stockhausen's ensemble for performances at the German Pavilion at Expo '70 in Osaka.He also prepared the recording of the collective composition "Ensemble", organized by Stockhausen for the Darmstadt Courses in 1967.