The document discusses the Expressionist composer Arnold Schoenberg and his pioneering atonal and twelve-tone compositions. It outlines his career in four periods, from his early Romantic style works through his development of techniques like the emancipation of dissonance, Sprechgesang vocal style, and ultimately twelve-tone serialism. Key works mentioned include Verklärte Nacht, Pierrot lunaire, and the pieces from his Opus 11 and the Society for Private Musical Performances he founded in 1918.