6.7 Harmonic Sequences

A harmonic sequence happens when a short group of chords repeats immediately at a higher or lower transposition, usually keeping the same root motion and voice leading each time. The interval of transposition stays constant, like always moving down a fifth or up a second, and a harmonic sequence often pairs with a matching melodic sequence in the upper voice.

Why This Matters for the AP Music Theory Exam

Recognizing harmonic sequences is mostly about pattern recognition, which shows up in both listening and notated music. On the multiple-choice section, you may hear or see a repeating chord pattern and need to identify it as a sequence and describe how it moves. In harmonic analysis with Roman numerals, spotting a sequence helps you label chords faster because the same pattern keeps repeating at a new pitch level. When you part-write or analyze a chorale-style passage, knowing the standard sequence patterns helps you predict the next chord and keep voice leading clean.

This topic also connects to melodic sequence work, since the two often happen together. Building fluency with both makes dictation, score analysis, and Roman-numeral realization more efficient.

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Key Takeaways

• A harmonic sequence is a chord pattern that repeats immediately at a consistent interval of transposition (for example, always down a fifth).
• Root motion direction is usually labeled in terms of fifths, thirds, or seconds; descending fifths, descending thirds, and ascending seconds are the most common.
• Down a fifth is the same root motion as up a fourth, and up a third is the same as down a sixth, so simplify to fifths, thirds, or seconds when labeling.
• The root moving up or down does not mean every voice moves that way; voice leading keeps each part in its range.
• Harmonic sequences often appear with a matching melodic sequence in the upper voices.
• The same voice-leading pattern from the first segment carries through each repetition, which makes the next chords predictable.

Understanding Harmonic Sequences

A harmonic sequence occurs when a segment of chords is followed immediately by one or more transpositions of the same segment. For example, you might start with a I-V progression in major, then transpose that pattern down a second to get vii°-ii, and keep going. The relative motion of the chords and the voice leading usually carry over into each repetition.

The interval of transposition stays a constant size. If the pattern moves up a third the first time, it keeps moving up a third for every following segment.

Ascending vs. Descending

Harmonic sequences can ascend or descend. In a descending sequence, the harmonies move down by some interval with each repetition. A common version is a descending-fifths sequence, where the roots move down a fifth each time, such as Am to Dm to G to C to F. An ascending-fifths version moves the root up a fifth each time, such as Am to Em to B° to F#.

Keep two things in mind:

• The root moving up or down does not force every note to move the same way. Good voice leading keeps each voice in its usual range and avoids voice crossing or overlap, so the actual notes may go up or down independently of the root.
• Down a fifth equals up a fourth, and up a third equals down a sixth. Always label sequences in terms of fifths, thirds, or seconds. If the root seems to climb by sixths, read it as a descending-thirds sequence instead. Do the same for anything labeled in fourths.

You can also use the upper voices to decide direction. If the melody mostly rises, you might call the sequence ascending; if it mostly falls, descending.

Common Types of Harmonic Sequences

Descending and Ascending Fifths Sequences

Descending-fifths sequences outline the circle of fifths and usually use two fifth-related chords per segment, with the pattern then descending by a second, such as I-V-vii°-ii in major. These can use all seventh chords, alternate triads and seventh chords, or alternate inversions of seventh chords.

When writing descending-fifths sequences with all root-position seventh chords, alternate complete and incomplete chords (dropping the fifth) to avoid parallels. Since the sequence follows the voice leading of the first segment, doubling the root in vii° and ii° chords is acceptable here.

Descending-fifths motion shows up in common functional moves like V-I, tonic to predominant (I-IV), and predominant to dominant (ii-V).

Ascending-fifths sequences follow the same idea but transpose the pattern up a second (for example, iii-vii-IV-I).

Descending Thirds Sequences

Descending-thirds sequences often appear in the predominant area (such as vi-IV-ii) or moving from predominant to dominant (such as ii-vii°6). Ascending-thirds sequences exist but are much less common. Thirds sequences usually avoid seventh chords.

Ascending Seconds Sequences and Parallel 6/5 Chords

Ascending-seconds sequences show up in tonic to predominant motion (I-ii), predominant to dominant motion (IV-V), and dominant to tonic motion (vii°-I). You also see them in deceptive motion from dominant to submediant (V-vi).

Parallel 6/5 chord sequences often move up or down by step. The interval pattern between outer voices can be plain, so composers frequently add a chain of suspensions or retardations. This often creates 7-6 suspensions when descending or 5-6 retardations when ascending.

When writing ascending seconds, watch carefully for parallel fifths.

Pachelbel-Style Sequences

A Pachelbel-style sequence follows a root progression of a descending fourth followed by an ascending second. The familiar Canon progression is I-V-vi-iii-IV-I-IV-V. When writing this kind of sequence, you can use all root-position chords or alternate root position and first inversion to get a stepwise descending bass line.

Other Sequence Labels You May See

Some theory resources name stock sequence patterns with terms like Fonte, Ponte, and Monte. Treat those as labels for common sequential motion, not as separate rules to memorize before you understand the root motion. If a question or score excerpt uses one of those names, translate it back into the same basic question: what chord pattern repeats, and by what interval does it move?

You may also see linear intervallic pattern (LIP) language, such as 10-6, 10-10, or 10-5 patterns. A LIP describes the repeated interval pattern between voices while the harmony sequences. It is useful for score analysis because it tells you what the outer voices are doing, but it should support the Roman-numeral analysis rather than replace it.

How to Use This on the AP Music Theory Exam

MCQ

When a passage repeats a chord pattern at a new pitch level, name it as a sequence and describe the root motion in fifths, thirds, or seconds. Simplify any "up a fourth" or "down a sixth" labels first. Use the melody direction as a clue for whether to call it ascending or descending.

Harmonic Analysis

In Roman-numeral analysis, find the first segment of the sequence, then expect the same pattern to repeat at the transposition interval. This lets you predict and label the following chords quickly instead of analyzing each one from scratch.

Part Writing

If you are realizing a figured bass or Roman-numeral progression that forms a sequence, carry the voice-leading pattern from the first segment through each repetition. For descending-fifths seventh-chord sequences, alternate complete and incomplete chords to avoid parallels, and watch for parallel fifths in ascending-seconds patterns.

Listening and Dictation

In aural work, listen for the same harmonic shape coming back immediately at a higher or lower level, often with a matching melodic sequence on top. Identifying the repeated unit helps you fill in chords and melody faster.

Common Misconceptions

• A sequence is not just any repeated chords. The pattern must repeat immediately at a consistent transposition interval. If the interval keeps changing, it is not a true sequence.
• An ascending or descending root does not mean every voice moves the same direction. Voice leading controls the actual pitches in each part.
• "Down a fifth" and "up a fourth" describe the same root motion. Label sequences using fifths, thirds, or seconds rather than fourths or sixths.
• A melodic sequence and a harmonic sequence are not the same thing, even though they often occur together. One refers to the repeated melodic segment and the other to the repeated chord segment.
• The repeated segment carries its voice leading with it, so you should not reinvent the part writing for each repetition. Match the original segment's pattern.

Related AP Music Theory Guides

• 6.6 Melodic Sequences
• 6.2 Embellishing Tones: Writing Passing Tones and Neighbor Tones
• Unit 6 Overview: Harmony and Voice Leading III (Embellishments, Motives, and Melodic Devices)
• 6.4 Embellishing Tones: Identifying and Writing Suspensions; Identifying Retardations
• 6.1 Embellishing Tones: Identifying Passing Tones and Neighbor Tones
• 6.3 Embellishing Tones: Identifying Anticipations, Escape Tones, Appoggiaturas, and Pedal Points