Melodic sequence

Sequence is a common compositional device that relies on a series of successively occurring rhythmic, melodic, and/or harmonic patterns. Melodic sequence occurs anytime a portion of music (both intervallic and rhythmic content) is immediately replicated at a different pitch level. The first iteration of a sequence is called the model, and each subsequent iteration is called a leg. Example 18-1 contains a transcription of a recording by Mitski that uses a melodic sequence. The model features intervals of a descending sixth followed by an ascending fifth, and each leg begins a third lower than the previous iteration.

Example 18‑1. Transcription of Mitski, “Washing Machine Heart,” 1:10–1:24

Listen to the full track on Spotify.

Learn about Japanese-American singer-songwriter Mitski (b. 1990) by reading her bio at last.fm.

Melodic sequences can be either real (exact) or tonal. Real sequences maintain the exact intervallic qualities in each leg of the sequence. Tonal sequences maintain the quantity (number) of each interval, but not the quality, in order to fit within a key. The melodic sequence in Example 18‑1 is tonal because all the notes are diatonic in the key of the excerpt (A major). It is rewritten as a real sequence in Example 18-2, using chromaticism to preserve the exact intervallic structure of the initial model (mi6 descending followed by P5 ascending) in each leg. Most melodic sequences we encounter in tonal music will be tonal, not real, sequences.

While melodic sequences are common in a variety of styles, they are especially common in Baroque music. The music of J. S. Bach, one of the most famous European composers of the Baroque era, features melodic sequences with great frequency. Example 18‑3 shows a representative passage, annotated to show three melodic sequences from Bach’s Violin Sonata in G minor. The first, in m. 90, states the model starting on B, and the leg that follows starts a step higher. The second sequence in this passage occurs in the following measure and contains the model starting on C, followed by no fewer than four complete legs, each starting a step lower than the previous one. The sequence breaks before the completion of what would have been the fifth leg. The final sequence in this passage occurs in m. 93. Each leg following the model begins a third lower than the previous segment.

Harmonic sequence

Sequences may also be harmonic. Harmonic sequence occurs when a repeating pattern of root motion appears in a harmonic progression. This list is not exhaustive, but three common harmonic sequences include root motion:

• by fifth (circle-of-fifths)
• down a fourth, up a second (↓4 ↑2)
• by falling thirds

Each of these types is shown in the examples below.

Melodic dictation with sequences

You can hone your aural skills by notating melodies that use melodic sequence. See nos. 23–27 in Appendix D for melodic dictations using sequence.

Uses of the mediant

Unlike all of the other diatonic triads we have studied, the mediant triad appears less often. It is perhaps the least versatile of all chords because it usually appears in one of the following specific contexts:

• Part of a harmonic sequence
• An extension of tonic function in the progression I – iii – IV – V (or i – III – iv – V in minor), often harmonizing a descending melody, with scale-degrees – – –

Example 18‑8 shows how the mediant triad works with the ↓4 ↑2 sequence, made famous by Pachelbel’s Canon. The mediant triad may appear in other sequences as well, such as the circle-of-fifths sequence.

Example 18‑9 shows the voice-leading context for the use of the mediant with the I – iii – IV – V progression.

Example 18‑10 uses this progression in the key of G major (I – iii – IV – V), and Example 18‑11 uses a similar progression in A major (I – iii – IV – I).

Occasionally the mediant triad functions as a substitute for dominant (this occurs in a handful of late 19th-century compositions, as well as a few pop tunes). However, since it shares scale degrees and with the tonic triad, and and with the dominant triad, it is generally a less effective and less clear means of conveying dominant function than the dominant or leading tone chords.