(b Vienna9 Feb 1885d Vienna24 Dec 1935). Austrian composer. Along with his teacher Arnold Schoenberg and fellow pupil Anton Webern in the years before and immediately after World War I, he moved away from tonality to write free atonal and then 12-note music. At once a modernist and a Romantic, a formalist and a sensualist, he produced one of the richest bodies of music in the 20th century, and in opera, especially, he had few equals.