Twelve-Tone System

Twelve-Tone System or Twelve-Note System, widely used approach to writing music, developed by the Austrian composer Arnold Schoenberg. He devised the system between about 1908 and 1923 while searching for a principle around which to organize atonal music (music that avoids a central keynote and all key relationships). The composer first arranges the 12 notes of the chromatic scale in a particular order, forming a row of notes. A composition is then built by using each note of the row in turn, beginning again with the first note each time the end of the row is reached. Notes may be used one after another, as melody, or simultaneously, as chords. They may be placed in as high or low a range as desired and given to whatever instrument or voice the composer chooses. The row may also be used in three variations: retrograde (played backwards from end to beginning); inversion (played upside down, so that an upwards leap becomes a downwards leap of the same interval and vice versa); and retrograde inversion (upside down and backwards). The original row and any variations can also be transposed to higher or lower pitches.

Schoenberg's first works to use the new technique were the Five Piano Pieces, op. 23, the Serenade for Septet, op. 24, and the Piano Suite, op. 25, all completed in 1923. Schoenberg's twelve-tone music was often emotional and expressionistic. His students, the Austrian composers Alban Berg and Anton Webern, used the system in striking ways. Berg, whose style was also expressionistic, often combined twelve-tone and traditional tonal elements, sometimes constructing twelve-tone rows that contained (instead of avoided) traditional chords. Webern used the row more abstractly, often splitting it and recombining its sections, and his musical style was based on clarity and conciseness. Before World War II, few composers outside Schoenberg's immediate circle used the twelve-note system, though two important exceptions were Ernst Krenek and Frank Martin.

The twelve-tone system was the first and most famous formulation of the concept of serialism, which is the most far-reaching innovation of 20th-century music. Serialism is the repetition and variation of a given sequence (a series) in any musical element—not only pitch, but also rhythm, tone colour, and even blocks of sound or levels of loudness and softness. This extension of the concept derived from Webern, who of all the original group had applied the system most rigorously. His music had a direct influence during the war on Olivier Messiaen, and after the war on Messiaen's pupils at the Paris Conservatoire Karlheinz Stockhausen, Iannis Xenakis and Pierre Boulez, among others. “Total serialism” can be seen in relatively few works, such as Messiaen's Livre d'orgue for organ, and Boulez's Structures I for two pianos, both from 1951. Since the 1930s, European émigrés, principally Schoenberg himself, had been introducing serial ideas to the United States, and in the 1950s an influential group of composers centred around Milton Babbitt and Roger Sessions at Princeton University began to establish a rigorously serialist school of composition, which has formed an important strand of US musical life ever since.

Since the 1950s composers have used the concepts of serialism with ever-increasing freedom, absorbing them into their personal styles and developing them in their own ways as one aspect of technique among many others.