Sequence (music)

In music, a sequence is the restatement of a motif or longer melodic (or harmonic) passage at a higher or lower pitch in the same voice. It is one of the most common and simple methods of elaborating a melody in eighteenth and nineteenth century classical music (Classical period and Romantic music). Characteristics of sequences:

It is possible for melody or harmony to form a sequence without the other participating.

A real sequence is a sequence where the subsequent segments are exact transpositions of the first segment, while a tonal sequence is a sequence where the subsequent segments are diatonic transpositions of the first. The following passage from J.S. Bach demonstrates both kinds of sequence at work:

A rhythmic sequence is the repetition of a rhythm with free use of pitches:

A modified sequence is a sequence where the subsequent segments are decorated or embellished so as to not destroy the character of the original segment:

A false sequence is a literal repetition of the beginning of a figure and stating the rest in sequence:

A modulating sequence is a sequence that leads from one tonal center to the next, with each segment technically being in a different key in some sequences:

The above passage starts in F major and modulates to B flat major and then, via the chord of G to C major. Sometimes sequential passages combine more than one of the above characteristics. In the third and fourth bars of the “Air” from J.S. Bach’s Orchestral Suite No. 3 in D major, the violin part forms a tonal sequence with the notes modified to fit the harmony, while the intervals in the bass line are unchanged, creating a real sequence. The whole passage also forms a modulating sequence, starting in D major and moving through E minor at the start of the fourth bar:

A sequence can be described according to its direction (ascending or descending in pitch) and its adherence to the diatonic scale—that is, the sequence is diatonic if the pitches remain within the scale, or chromatic (or non-diatonic) if pitches outside of the diatonic scale are used and especially if all pitches are shifted by exactly the same interval (i.e., they are transposed). The non-diatonic sequence tends to modulate to a new tonality or to cause temporarily tonicisation.

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