Morton Feldman was an American composer. A major figure in 20th-century classical music, Feldman was a pioneer of indeterminacy in music, a development associated with the experimental New York School of composers also including John Cage, Christian Wolff, and Earle Brown. Feldman's works are characterized by notational innovations that he developed to create his characteristic sound: rhythms that seem to be free and floating, pitch shadings that seem softly unfocused, a generally quiet and slowly evolving music, and recurring asymmetric patterns. His later works, after 1977, also explore extremes of duration.