The term chromatic comes from the Greek word chroma, meaning “color.” A diatonic scale consists of seven (out of twelve possible) pitches within an octave. The chromatic scale uses all twelve pitches within an octave, using all the “colors,” so to speak. Note in the example below that sharps are used to notate the ascending chromatic scale; flats to notate the descending scale. This avoids the necessity of using natural signs to cancel previous accidentals.
ascending/descending chromatic scale
When writing a chromatic scale, avoid the mistake of repeating a note in the chromatic scale where the natural half steps occur. In the following example, E# is the enharmonic equivalent to F; B# is the enharmonic equivalent to C. E# and B# should not be included in the chromatic scale. Also, note that a chromatic scale can begin on any pitch.
incorrect notation of a chromatic scale
Following is the famous “Habanera” from Bizet’s opera Carmen. Each melodic phrase begins with a chromatic descent.