Morton Feldman (January 12, 1926 – September 3, 1987) was an American composer, born in New York City. A major figure in 20th-century music, Feldman went through several compositional phases. He was a pioneer in aleatoric music and indeterminate music, and in music requiring improvisation. His works are characterized by quietness, slowness, and often by their extreme length, especially in his later music.