Chromaticism

chromaticism

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 Frédéric Chopin, did not threaten the perception 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 Arnold Schoenberg and his followers in the early 20th century.

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Chromaticism 

the augmenting or diminishing, by a semitone, of a degree in a diatonic scale, thereby heightening the degree’s tendency to gravitate toward an adjacent degree. A chromatic semitone lies between a diatonic degree and its augmented or diminished variant. The difference between a chromatic semitone and a diatonic semitone is that the notes of the chromatic semitone belong to a single degree; thus, the chromatic semitone C–C sharp contrasts with the diatonic semitone C–D flat. Chromatic alteration is indicated by signs of alteration, or accidentals. Alteration is more common than chromaticism, since every chromaticism is an alteration, but not every alteration is chromatic; an alteration in C major, for example, may lead to the establishment of a new key. Chromatic alteration is a real change in a diatonic degree in one voice; alteration occurs when the diatonic variant of that degree is given before the altered note in another voice or does not precede it at all.