Arnold Schoenberg (1874-1951) was an Austrian composer whose discovery of the "method of composition with twelve tones" radically transformed 20th-century music.

The early music of Arnold Schoenberg represents the culmination of romantic musical ideals. His gigantic cantata Gurre-Lieder is, together with Gustav Mahler's Eighth Symphony, one of the last great works in the monumental style. It seemed impossible for music to develop any further in this direction. Thus, Schoenberg became one of the first 20th-century composers to write for small, specialized chamber ensembles. He transcended traditional tonal limitations and began to write "atonal" or "pantonal" music without a key center. This new style offered much freedom, but there was need of a system to control the new harmonic material thus made available.

After a period of experimentation, Schoenberg developed such a system: the method of composition with twelve tones. So far-reaching were the results of this discovery that...