The chromatic scale is a musical scale with twelve equally spaced pitches, each a semitone apart. A chromatic scale is a nondiatonic scale having no tonic due to the symmetry of its equally spaced tones.
Chromatic scale on C: full octave ascending and descending Play (help·info)
The most common conception of the chromatic scale before the 15th century was the Pythagorean chromatic scale. Due to an imperfect 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.
Although composers have not been consistent, music theorists have divided the notation of any chromatic scale into a variety of ways:
Ascending and descending:
Harmonic and melodic:
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 lowered 2nd and raised 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.