Chromaticism

Chromaticism is the use of pitches outside a composition’s prevailing diatonic scale. It can enrich melody and harmony, intensify expression, or weaken a clear sense of key.

Chromatic scale: A twelve-pitch collection that divides the octave into semitones in common Western tuning. It supplies the full pitch vocabulary from which chromatic notes depart from a diatonic scale.
Diatonic scale: A seven-note scale organized from five whole steps and two half steps within an octave. Chromaticism is defined by pitches lying outside this prevailing seven-note framework.
Leading tone: The scale degree a semitone below the tonic, with a strong tendency to resolve upward to it. Chromatic leading tones can create sharper resolution than the diatonic scale provides.
Diatonicism: The use of notes and harmonies drawn primarily from a diatonic scale. It provides the scale-bound alternative against which chromaticism is defined.
Altered chord: A chord containing one or more notes chromatically changed from a common chord form. Chromaticism can transform a diatonic chord by raising or lowering one of its tones.
Semitone: The smallest interval commonly used in Western equal-tempered music, equal to one-twelfth of an octave. Many chromatic alterations move a scale degree by one semitone.
Chromatic modulation: A change of key connected by a chromatic alteration in one or more notes. It uses chromatic pitches to make a transition between tonal centers.
Atonality: Music that lacks a governing tonal center or traditional hierarchy of tonic and related keys. Chromaticism can enrich tonal music without abolishing the tonal center that atonality rejects.
Secondary dominant: A dominant-function chord that temporarily tonicizes a key other than the composition’s tonic. Its applied leading tone introduces chromaticism while briefly pointing toward another chord.
Scale degree: A note’s numbered position within a scale, often described by its melodic and harmonic function. Chromaticism alters scale degrees, changing their sound and often their directional pull.

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