Harmonic Sequences

Harmonic Sequences

• Harmonic sequences are short, melodic-harmonic patterns that are repeated on different scale steps. The strong linear or con-trapuntal direction of the melodic sequence dictates the chord progression and therefore overrides the chords’ normal tendencies.

• Harmonic sequences consist of a two-chord pattern that is repeated.

Harmonic Sequences:

• Occur in both diatonic and chromatic versions (i.e., using secondary function chords).

• May use seventh chords instead of triads for one or both chords of the initial pattern.

• May alternate between root-position chords and inversions. However, once the initial pattern is stated, the pattern tends to be upheld.

The Four Primary Harmonic Sequences.

•Descending Fifths (aka circle of 5ths)•Ascending Fifths•Descending 5-6 (aka Falling Thirds)•Ascending 5-6 (rising by step)

The Descending 5ths Sequence:

• Is the most important (and most often used) of the four sequence types, because it is based on the most important chord progression in tonal music: the descending fifth.

• It often ‘cycles’ through all seven chords of the scale.

• It’s found in a variety of forms: diatonic, chromatic, using inversions, and 7th chords.

• Each repeated pattern is a step lower than its predecessor.

The initial pattern of a descending 5ths sequence may be as simple as:

When the pattern repeats, it appears a step lower. Notice that each voice part’s voice leading in the initial pattern is maintained.

Two more repetitions of the pattern and the chord progression cycles all the way back to I.

Here’s the same circle of 5ths sequence, but this time stated in minor:

Here’s a descending 5ths sequence in the minor

mode:

The Ascending 5ths Sequence

• Because root motion by ascending 5ths does not establish a sense of tonality, this sequence does not cycle through all seven chords.

• In the major mode the sequence usually takes the form of: IÿV, iiÿvi, iii. Note that if the sequence continued, the next two chords, viiøÿIV create root progression by tritone.

• In the minor mode, the first repetition of the pattern would be iiøÿVI, root motion by tritone, so these two chords are skipped and the sequence continues: iÿV | IIIÿVII, ivÿi

• When the initial pattern repeats, it will appear a step higher.

The Ascending 5ths sequence in the major mode: basic voice leading

Here’s an example of an ascending 5ths sequence in the major mode. As commonly happens, the sequence breaks off when we reach the iii chord.

In this excerpt Handel extends the ascending 5th sequence one more fifth than usual, but he changes the expected chord (viiø) into a secondary dominant (V/iii), which here acts as back-relating dominant. That is, it’s the secondary dominant of the chord in front of it.

Here’s an ascending 5ths sequence in the minor mode. As is typical, the progression iiøÿVI is omitted.

The descending 5-6 sequence (aka “falling 3rds”) is driven by a stepwise melodic line, usually in the bass. The soprano is set either in parallel 10ths with the bass, or it creates an alternating pattern of 10-6 intervals. With each repetition, the pattern appears a 3rd lower.

But the term “5-6” arises because of alternating intervals of a 5th and 6th between the bass and one of the upper voices. The sequence yields the progression. Note the pattern of alternating root-position and first-inversion chords.

Here’s an example in the major mode. Note that the sequence starts on the upbeat.

The descending 5-6 sequence is also commonly found in a root-position variant. All the chords are in root position and the soprano almost always descends by step.

The most famous rendition of the root-position version of the descending 5-6 sequence is Pachelbel’s Canon in D. But here’s the same sequence used by Handel. (The dotted ties indicate implied suspensions.)

The ascending 5-6 sequence also gets its name from a pattern of alternating intervals of the 5ths and 6ths Note: the pattern can also be expressed as 6-5.

This example starts with the interval of a 6th and is most visible in the bass and tenor parts.

The ascending 5-6 sequence is commonly found in a root-position variant. The root-position variant pro-vides for a much more interesting bass line.