Arnold Schoenberg pioneered the technique of using each of the twelve pitches of the chromatic scale in a serial order often called a tone row or set. This gives each pitch more or less equal importance and eliminates any sense of key center. The method was used in the early twentieth century by the composers of the Second Viennese School — Alban Berg, Anton Webern, Hanns Eisler and Schoenberg himself.
While the technique can be applied very strictly in written compositions, a freer application of twelve-tone technique making use of partial sets, inversion, retrograde, and retrograde-inversion techniques have been used by many composers and can be applied in improvisation.
