Dodecaphony, also known as twelve-tone serialism, is a compositional technique in which each of the twelve notes of the chromatic scale is sounded as often as the others. It is a type of serialism, a broad category of compositional techniques that use rows of some musical elements, such as pitch or note duration or rhythm in which such elements are arranged so that each is played in a sequence selected by the composer.
In the case of pitch, one note from each pitch class is contained in each row. Although notes can have different durations and different dynamics and fall on different beats, every note is included, thus pushing the work away from tonality. Although serial music is not necessarily atonal, it is closely associated with it.
Twelve-tone serialism was devised by Austrian composer Arnold Schoenberg (1874–1951) and is associated with the Second Viennese School composers, who were its main users during the first decades of its existence. This technique gradually increased in popularity and eventually became widely influential on 20th century composers, including some who had actively opposed it.