In music, the use of all 12 tones, especially for heightened expressivity.
A standard key or mode principally employs 7 tones, leaving 5 tones for discretionary use. Use of all 12 tones in a given piece increased in the 18th and 19th centuries. Strictly controlled chromaticism, as in the ornamentation of tonality . However, from the mid-19th century on, complaints were heard with ever greater frequency that it was difficult to perceive what a given piece's tonal centre was, the chromaticism in the works of Richard Wagner being the most notorious. The virtual breakdown in tonality in the works of advanced composers led to the free atonality of {{link=Schoenberg, Arnold Franz Walter">Arnold Schoenberg and his followers in the early 20th century.