# of pitch classes: 12
The chromatic scale is a musical scale with twelve pitches, each a semitone or half step apart. "A chromatic scale is a nondiatonic scale consisting entirely of half-step intervals," having, "no tonic," due to the symmetry or equal spacing of its tones.
Chromatic scale on C: full octave ascending and descending
The most common conception of the chromatic scale before equal temperament was the Pythagorean chromatic scale, which is essentially a series of eleven 3:2 perfect fifths. The twelve-tone equally tempered scale tempers, or modifies, the Pythagorean chromatic scale by lowering each fifth slightly less than two cents, thus eliminating the Pythagorean comma of approximately 23.5 cents. Various other temperaments have also been proposed and implemented.
The term chromatic derives from the Greek word chroma, meaning color. Chromatic notes are traditionally understood as harmonically inessential embellishments, shadings, or inflections of diatonic notes.
Although composers have not been consistent, music theorists have divided the notation of any chromatic scale into a variety of ways:
The ascending chromatic scale
The descending chromatic scale
The harmonic chromatic scale
The melodic chromatic scale
The harmonic chromatic scale has a set form that remains the same whether ascending or descending and regardless of key signature. It is created by including all the notes from both the major and minor (melodic and harmonic) scales and then adding the flattened 2nd and sharpened 4th degrees from the starting note. The harmonic chromatic scale therefore has every degree of the scale written twice, apart from the 5th and the key-note or starting note at the top or bottom.
The melodic chromatic scale has no set form that is agreed upon by all. However their form is dependent upon major or minor key signatures and whether the scale is ascending or descending. The image above therefore is only an example of the melodic chromatic scale, as it has no set form. That no scale degree should be used more than twice in succession (for instance G flat - G natural - G sharp) is however a principle upon which most are agreed.
Here is the standard keyboard fingering for a chromatic scale; where 1 means the thumb; 2 the index finger; 3 the middle finger:
The ancient Greeks wrote of three genera of tetrachords: the diatonic, the chromatic, and the enharmonic. Some theorists, such as Ptolemy, assigned specific frequency proportions to these genera and others, such as Aristoxenus, did not. The tetrachords proceeded in descending order, the diatonic genus filling a perfect fourth with two whole tones and a semitone, the chromatic genus filling a perfect fourth with a minor third and two semitones, and the enharmonic genus filling a perfect fourth with a major third and two quarter tones.
The ancient Chinese chromatic scale is called Shi Er Lü.
1. ^ a b c Benward & Saker (2003). Music: In Theory and Practice, Vol. I, p.47. Seventh Edition. ISBN 978-0-07-294262-0.