Arnold Schoenberg or Schönberg (13 September 1874 – 13 July 1951) was an Austrian and American avant-garde composer, music theorist, teacher and writer. He was among the first modernists who transformed the practice of harmony in 20th-century classical music, and a central element of his music was its use of motivic processes as a means of coherence. He propounded concepts like developing variation, the emancipation of the dissonance, and the "unity of musical space".
Schoenberg's early works, like Verklärte Nacht (1899), represented a Brahmsian–Wagnerian synthesis on which he built. Mentoring Anton Webern and Alban Berg, he became the central figure of the Second Viennese School. They consorted with visual artists, published in Der Blaue Reiter, and wrote atonal, expressionist music, attracting fame and stirring debate. In his String Quartet No. 2 (1907–1908), Erwartung (1909), and Pierrot lunaire (1912), Schoenberg visited extremes of emotion; in self-portraits he emphasized his intense gaze.