Chromatic Sequences

A chromatic sequence is a sequential harmonic pattern in which at least one voice moves by half step at each repetition, or in which the transpositional interval between units is not a diatonic step but a chromatic one (such as a minor second or tritone). Chromatic sequences share the same basic logic as diatonic sequences — a unit of harmony or melody is transposed and repeated — but they depart from the diatonic scale to produce intensified color and the sensation of moving through harmonic space more quickly.

One of the most common chromatic sequence patterns is the descending-fifth sequence with chromatic quality changes. For example, a series of dominant seventh chords moving down by half step (e.g., C7–B7–B♭7–A7) maintains the interval of a tritone within each chord while the roots descend chromatically. This is sometimes called a "chromatic mediant sequence" or a "planing" sequence, and it appears frequently in late Romantic and jazz contexts. Each chord feels locally like a dominant, but the roots move in a way that has no single tonal goal.

Another important type is the sequence of parallel chords (planing), where a chord quality is maintained exactly and transposed chromatically. Parallel major triads descending by whole steps, or parallel dominant seventh chords moving through the chromatic scale, strip chords of their individual tonal functions and treat them as color blocks. This technique is strongly associated with Debussy and impressionism, where harmonic movement is governed by voice-leading smoothness and timbral effect rather than functional direction.

When analyzing chromatic sequences, identify the repeating unit (the "model") and the transposition interval. Then note whether the voice-leading within each unit is smooth (step-wise or half-step motion) or leaping. The power of chromatic sequences lies in the tension between the pattern's regularity and its departure from diatonic norms: the ear hears order, but that order does not resolve toward a single tonic in the expected way.