The chromatic scale might be used in what field?

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.