Arnold (ˈarnɔlt). 1874–1951, Austrian composer and musical theorist, in the US after 1933. The harmonic idiom of such early works as the string sextet Verklärte Nacht (1899) gave way to his development of atonality, as in the song cycle Pierrot Lunaire (1912), and later of the twelve-tone technique. He wrote many choral, orchestral, and chamber works and the unfinished opera Moses and Aaron