Arnold Schoenberg (pronounced [ˈaːrnɔlt ˈʃøːnbɛrk]) (13 September 1874 – 13 July 1951) was an Austrian and later American composer, associated with the expressionist movement in German poetry and art, and leader of the Second Viennese School. He was the most important and most influential composer of the 20th century. Schoenberg was known early in his career for successfully extending the traditionally opposed German Romantic traditions of both Brahms and Wagner, and later and more notably for his pioneering innovations in atonality.