Arnold Franz Walter Schoenberg ( originally written SchÃ nberg ) ( September 13 , 1874 â `` July 13 , 1951 ) was an Austrian born composer . Arnold Schoenberg ( ; 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 .