In the early 1970s Feldman increasingly turned his attention to works for orchestra, in most cases combined with a solo instrument, like Piano and Orchestra (1975). One aspect that was important to him in all of these works was a research into sound, an "unceasing effort to create, by way of exclusion and integration, by operating with colored projection surfaces and various spatial levels, a kind of self-supporting structure elastic enough to take up the exactly fixed initial impulse and continue it of its own accord." (Ulrich Dibelius) Durations II (1960) plays with durations and timbres of sound: "In each piece, the instruments start at the same time and are then free to find their own durations within the framework of a given general tempo." (Feldman)