|Number of pitch classes 12|
The chromatic scale is a musical scale with twelve pitches, each a semitone above or below another. On a modern piano or other equal-tempered instrument, all the semitones have the same size (100 cents). In other words, the notes of an equal-tempered chromatic scale are equally spaced. An equal-tempered chromatic scale is a nondiatonic scale having no tonic because of the symmetry of its equally spaced notes.
The most common conception of the chromatic scale before the 13th century was the Pythagorean chromatic scale. Due to a different tuning technique, the twelve semitones in this scale have two slightly different sizes. Thus, the scale is not perfectly symmetric. Many other tuning systems, developed in the ensuing centuries, share a similar asymmetry. Equally spaced pitches are provided only by equal temperament tuning systems, which are widely used in contemporary music.
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.
The chromatic scale may be notated in a variety of ways.
Ascending and descending:
The chromatic scale has no set spelling agreed upon by all. Its spelling is, however, often dependent upon major or minor key signatures and whether the scale is ascending or descending. The images above, therefore, are only examples of chromatic scale notations. As an abstract theoretical entity (that is, outside a particular musical context), the chromatic scale is usually notated such that no scale degree is used more than twice in succession (for instance G flat - G natural - G sharp).
The total chromatic (or aggregate) is the set of all twelve pitch classes. An array is a succession of aggregates. See also: Tone row.
In 5-limit just intonation the chromatic scale, Ptolemy's intense chromatic scale, is as follows, with flats higher than their enharmonic sharps, and new notes between E/F and B/C:
9/8 and 10/9, 6/5 and 32/27, 5/4 and 81/64, 4/3 and 27/20, and many other pairs are interchangeable, as 81/80 (syntonic comma) is tempered out. These are 19-EDO just intonation approximations.
In Pythagorean tuning (3-limit just intonation) the chromatic scale is tuned as follows, with sharps higher than their enharmonic flats:
These are 17-EDO Pythagorean tuning approximations.