Three composers who made frequent use of tone clusters for a wide variety of ensembles are Giacinto Scelsi, Alfred Schnittke—both of whom often worked with them in microtonal contexts—and Lou Harrison. Scelsi employed them for much of his career, including in his last large-scale work, "Pfhat" (1974), which premiered in 1986. They are found in works of Schnittke's ranging from the Quintet for Piano and Strings (1972–76), where "microtonal strings fin tone clusters between the cracks of the piano keys," to the choral "Psalms of Repentance" (1988). Harrison's many pieces featuring clusters include "Pacifika Rondo" (1963), Concerto for Organ with Percussion (1973), Piano Concerto (1983–85), Three Songs for male chorus (1985), Grand Duo (1988), and "Rhymes with Silver" (1996).