Alteration
In music alteration, an example of chromaticism, is the use of a neighboring pitch in the chromatic scale in place of its diatonic neighbor such as in an altered chord. This should not be confused with borrowing (as in borrowed chord), in which pitches or chords from the parallel key are used in place of those of the original key. Altered notes may be used as leading tones to emphasis their diatonic neighbors.
For example, an altered dominant or V chord may be Gb-B-D#:
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Altered_dominant_chord_C_major.PNG
Altered dominant chord C major