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I'd like help understanding the concept of sequences. I know it is considered a form of repitition, but not much else.

Below is an excerpt from Bach's Invention in Dm. Invention in Dm

I am told this excerpt includes both Harmonic and Melodic Sequences, but I am not sure how to identify them. What exactly in this score is a sequence, and how so?

Mostly, I would like a general explaination for what a Sequence is. If the difference between what melodic and Harmonic Sequences could also be explained, I would appreciate it.

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  • I am not sure which questions to ask based on the textbook. Instead of offering a definition for terms, it shows an excerpt of sheet music, followed by a list of terms and what measure they occur in. Nov 15, 2023 at 4:35
  • Weird. What is the textbook? Someone on the site may have a copy and be able to shed some light.
    – Aaron
    Nov 15, 2023 at 4:46
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    The Musician's Guide to Theory and Analysis, 4th Edition from W. W. Norton & Company. Nov 15, 2023 at 4:48
  • It seems to assume some topics are already understood, which would be fine for someone with previous training in theory. Sadly, that is not me. Nov 15, 2023 at 4:50
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    In that case, I suggest the following: rewrite the current post, or create a new one, posting one of the book's musical examples and asking for an explanation of what in the score comprises a sequence. You could also ask for a general definition, to ensure answers aren't overly specific. Depending on the answers you get, either your remaining questions will be addressed, or you can ask them separately.
    – Aaron
    Nov 15, 2023 at 5:18

1 Answer 1

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Sequence

A sequence is a musical pattern that is repeated in transposed form.

Melodic vs. Harmonic (a.k.a. Tonal vs. Real)

In a melodic sequence, the literal pattern is repeated.

In a harmonic sequence, the harmonic pattern (e.g., the chord progression) is repeated, but the specific note pattern might change.

In the Bach example, measures 7 and 8 form a musical unit — a pattern — that is repeated in measures 9 and 10, transposed downward by a major second.

Similarly, measures 10 and 11 form a pattern which is then repeated in measures 12 and 13 in measures 14 and 15, also transposed down a major second.

Both are examples of melodic sequences, since the notes themselves are all transposed. Measures 7–10 can also be considered a harmonic sequence, since the harmonic pattern of moving up a perfect fourth (from D to G, then C to F). Measures 11–13 can also be considered a harmonic sequence, since the chord pattern is transposed by fourths, even though the pattern shifts by an augmented fourth, but the transposed repetition moves by a perfect fourth.

Diatonic vs. Chromatic

In a diatonic sequence, it is permitted to make adjustments in the transposed repetitions so that the primary key remains unchanged.

A chromatic sequence is one in which pitches/harmonies from outside the main key can be used when required to keep the interval content of the pattern intact.

In the Bach example, both sequences are diatonic. Notice that the first two notes in the measure 7 pattern are F-D — a minor third. But in the repetition at measure 9, then first two notes are E-C — a major third. In a chromatic sequence, the first two notes of measure 9 would be E-C#, preserving the minor third in the pattern.

Measure 10–13 also comprise a diatonic sequence. For example, the harmony in the pattern moves by an augmented fourth from Bb to E. In a chromatic sequence, the transposed repetition would move from A to D# rather than the diatonic A to D.

Naming

Sequences are identified according to their level of transposition and sometimes root movement. The sequence in the Bach example are both descending second sequences and could also be identified as +4/-5.

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  • The first bit is non-standard, at least according to the common music theory literature. By default, a "sequence" (no other specification) is usually assumed to have repeated harmony. A "melodic sequence" is thus a pattern where the melody repeats, but with potentially differing harmonies. Cf. Harvard Dict. of Music: "A sequence is called melodic when the repetition occurs in the melody only..., harmonic if similar repetitions occur in all the parts." Oxford Comp. "If the repetition is of only in the melody with changed harmony, it is called a melodic sequence."
    – Athanasius
    Feb 19 at 1:52
  • Also, "melodic sequences" can be either real or tonal, depending on whether they follow the exact intervallic pattern from the melody (real) or modify the pattern to fit the scale (tonal). Harmonic sequences, on the other hand, have nothing to do with real vs. tonal and instead just imply that the harmony follows the sequential pattern up and down along with the melody. (Some sources will insist "harmonic sequences" have same melodic and harmonic patterns, while others would say "harmonic sequences" might have a varied melody but a consistent chord sequence.)
    – Athanasius
    Feb 19 at 1:54

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