Harmonic Sequences and Circle Progressions That Modulate

Repetition with transposition is the oldest engine in harmony. A short pattern restated a step lower, then again, carries the music forward with no new material, and the regularity lets listeners track long spans of modulatory travel without losing their place.

#The descending-fifth sequence

The most important sequence moves every root down a fifth. In C: Dm7 G7 C F Bø Em Am, each chord the ii of the next link. With seventh chords throughout, the chain runs itself: every seventh resolves down by step into the third of the following chord.

Four links of the chain appear above, each seventh falling into the next root’s third. Continue the pattern and it cycles through every diatonic seventh chord before returning to the start. Corelli, Vivaldi, and Bach built entire development passages from this single device.

Applied dominants intensify the chain. Turning each link into a V7 of the next (A7 Dm7, D7 G7, G7 C) sharpens every arrival and pushes the music flatward or sharpward depending on direction. The secondary dominant vocabulary is essentially this sequence with the transient tonicizations made explicit.

Melodic patterning matters as much as the roots. A true sequence repeats its melodic figure at each level, transposed exactly (real sequence) or adjusted to stay diatonic (tonal sequence). Real sequences modulate almost immediately; tonal ones can circle for bars before the accidentals accumulate into a new key.

#The ascending 5-6 pattern

Ascension needs a different mechanism, because rising fifths sound abrupt in chains. The standard ascending sequence alternates root-position and first-inversion triads over a stepwise climbing bass: C D E F with figures 5-6, 5-6. Each bass step carries first a fifth then a sixth above it.

The bass above climbs C D E F while the figures alternate, producing smooth contrary motion between outer voices. The pattern extends as far as the range allows and typically spans a fourth or fifth before cadencing. Handel marches and Mozart developments use it wherever the music must gain ground steadily.

Voice leading stays clean because the six chords are first inversions approached by step, the safest inversion in the style. Parallel fifths threaten only if the figures are misapplied; keeping strict alternation of 5 and 6 positions prevents them automatically.

A variant alternates 6/3 with 6/4 over the rising bass for a more floating texture, and another breaks the ascent into groups of three for a lilting compound feel. The principle never changes: stepwise bass plus alternating figures equals effortless climb.

#The Pachelbel loop and its children

Pachelbel’s Canon grounds its variations on eight chords: I V vi iii IV I IV V. The bass descends stepwise from tonic to dominant while the upper voices cycle through suspensions above it. The loop repeats without cadencing for the entire piece.

The progression survives because its voice leading is nearly perfect. Each chord connects to the next by step or common tone, the bass descent feels inevitable, and the final V loops back to I without needing a full close. Pop music rediscovered the loop independently: dozens of hits run I V vi IV (a four-chord compression) or the full eight-chord cycle under unrelated melodies.

Hear the four-chord compression that powers modern pop choruses.

Variants rotate the starting point (vi IV I V is the sensitive progression of countless ballads) or substitute applied chords at the turnaround. Recognizing the family resemblance turns radio listening into analysis practice: name the rotation, spot the substitutions, and the production choices become legible.

#Sequences that travel

Extended sequences modulate by accumulation. Each applied dominant or chromatic alteration nudges the center, and after several legs the music sits in a new key with no formal pivot. The modulation strategies account treats sequences as the gradual-transit lane: slower than a pivot chord, smoother than a direct jump.

Descending-third sequences travel flatward gracefully. Chains of major triads a third apart (C A flat F D flat) glide down by chromatic voice leading, each chord sharing two tones with the next. Film music and late Romantic symphonies use these chains for dreamlike drift, and the hexatonic logic behind them rewards separate study.

Ascending sequences with real transposition modulate almost at once, since exact repetition preserves the pattern’s accidentals against the home key. A two-chord model repeated up a step three times lands a third higher with a new signature implied. Development sections exploit this relentlessness: state the model in the home key and let the mechanism carry it somewhere far.

The return journey usually abandons sequence for cadence. After the pattern breaks, a standing dominant or a circle progression re-establishes the home key. Sequence travels, cadence arrives: that division of labor organizes most tonal development sections.

#Where sequences mislead people

Students call any repeated progression a sequence. Repetition alone is looping; sequence requires transposition of the pattern to new pitch levels. The Pachelbel loop repeats but does not transpose, so it is an ostinato progression, not a sequence in the strict sense. Terminology matters because the two devices do different formal work.

A second confusion treats sequences as primitive filler. Poorly written sequences do sound mechanical, but the masters vary the patterning: rhythmic displacement, melodic decoration, fragmentation of the model across legs. A Bach sequence often hides its mechanism under surface variety so complete that analysis must strip the figuration to expose the legs.

Voice-leading errors cluster in sequences because the pattern invites inattention. Each leg must still avoid parallels and resolve sevenths; the transposition preserves good voice leading but also preserves mistakes. Check one leg carefully and the pattern guarantees the rest, for better or worse.

#What to do with it

Write a descending-fifth sequence in four voices, four links long, with seventh chords throughout. Check that every seventh resolves down by step and no parallels slip in. Then rewrite the same span with applied dominants and note how the accidentals pull the center flatward.

Compose an eight-bar ascending passage on the 5-6 pattern over a bass climbing a fifth. Add a simple melody that repeats its shape at each level. The result should sound like Handel on autopilot, which is the point: the pattern carries the craft while you attend to the surface.

Finish by analyzing a development section from a Mozart piano sonata. Mark the sequence models, count the legs, and identify where the pattern breaks into cadential harmony. Then trace the key journey the sequence accomplished on the map in functional harmony. Seeing a two-bar model transport the music across three key signatures shows why sequences, not themes, do the traveling in sonata form.

Questions

What is a harmonic sequence?

A harmonic sequence repeats a short chord-and-melody pattern at steadily rising or falling pitch levels. The pattern, called the model, sets the interval of transposition, and each repetition is called a sequence leg. Baroque music runs on them.

What is the difference between a sequence and a circle progression?

A circle progression moves roots by descending fifth, which may or may not repeat a melodic pattern. A sequence repeats the pattern as well as the root motion. All sequential circle progressions are sequences, but not all circle progressions bother with exact patterning.

Why do sequences often modulate?

Repeating a pattern at new pitch levels introduces accidentals the home key cannot absorb, and the ear eventually accepts a new tonic. Applied dominants inside the pattern accelerate the drift. Composers use sequences to travel and cadences to arrive.

What is the Pachelbel progression?

The eight-chord loop I V vi iii IV I IV V in major, famous from Pachelbel's Canon. It combines stepwise bass descent with alternating root motion, and its variants underpin hundreds of pop songs.