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A seventh chord has four notes, so what are its inversions and how do we figure each one?

Topic 3.4 Seventh Chord Inversions and Figures: identify the four positions of a seventh chord and label them with figured-bass symbols (7, 6/5, 4/3, 4/2).

A focused answer to AP Music Theory Topic 3.4, covering the four positions of a seventh chord (root position, first, second, third inversion), the figured-bass symbols (7, 6/5, 4/3, 4/2), how the figures count intervals above the bass, and identifying the chordal seventh, with a worked inversion.

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  1. What this topic is asking
  2. Four positions, four figures
  3. How the figures work
  4. Why finding the seventh matters
  5. Reading a seventh-chord inversion
  6. Try this

What this topic is asking

The College Board (Topic 3.4) wants you to identify the inversion of a seventh chord from the chord tone in the bass and to label it with the correct figured-bass symbol. Because a seventh chord has four notes, it has four positions: root position and three inversions.

Four positions, four figures

As with triads, the inversion is decided only by the lowest sounding chord tone, not by the spacing or doubling of the upper voices. Read from the bass note up.

How the figures work

A useful pattern is that the figures shrink as the inversion deepens: the top figure goes 7, 6, 4, 4 and the chord becomes progressively less stable. Third inversion (4/2) is the least stable because the chordal seventh, a dissonance, is in the bass and must resolve down by step to the next chord's bass note.

Why finding the seventh matters

The central idea is that the chordal seventh is the active, dissonant tone, and in every inversion it must resolve down by step. Identifying the seventh tells you the figure, the inversion, and what happens next. In third inversion the seventh is in the bass, so the bass itself must step down to the next chord, which is why a dominant seventh in third inversion (V4/2) resolves to a first-inversion tonic (I6): the bass seventh falls to the third of the tonic. Hearing this in dictation and writing it in part-writing both depend on first locating the seventh. Inversion also shapes the bass line: a composer can keep the bass smooth and stepwise by choosing inversions, so reading figures fluently lets you follow and reproduce that line.

Reading a seventh-chord inversion

To name the inversion, identify the chord and its four tones, then find the bass note and ask which chord tone it is. Root gives 7, third gives 6/5, fifth gives 4/3, seventh gives 4/2. Confirm by measuring the intervals above the bass.

Try this

Q1. Which chord tone is in the bass of a third-inversion seventh chord, and what is its figure? [1 point]

  • Cue. The seventh is in the bass; the figure is 4/2 (or just 2).

Q2. A D dominant seventh chord (D, F sharp, A, C) has F sharp in the bass. Name the inversion and figure. [2 points]

  • Cue. F sharp is the third, so the chord is in first inversion, figured 6/5.

Exam-style practice questions

Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

AP 2022 (style)1 marksSection I (multiple choice, written). A G dominant seventh chord (G, B, D, F) has F in the bass. What inversion and figure is this? (A) root position, 7 (B) first inversion, 6/5 (C) second inversion, 4/3 (D) third inversion, 4/2
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The correct answer is (D) third inversion, 4/2.

The chordal seventh of G dominant seventh is F. When the seventh is in the bass, the chord is in third inversion, figured 4/2 (or just 2). Above the bass F there is a fourth (F up to B) and a second (F up to G), giving the figures 4 and 2.

(A) root position (7) has the root G in the bass. (B) first inversion (6/5) has the third B in the bass. (C) second inversion (4/3) has the fifth D in the bass. The trap is forgetting that a seventh chord has four possible bass notes, so there are four inversions, not three.

AP 2023 (style)2 marksSection II (free response, notation). Notate a C dominant seventh chord in first inversion, name the pitch in the bass, and give the figured-bass symbol.
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A 2-point inversion question.

(1 point) A C dominant seventh chord is C, E, G, B flat. In first inversion the third, E, is in the bass, with G, B flat and C above it, so the bass note is E.
(1 point) The figured-bass symbol is 6/5, because above the bass E there is a sixth (E up to C) and a fifth (E up to B flat).

Markers reward placing the third (E) in the bass and the correct 6/5 figure. Putting the seventh (B flat) in the bass would be third inversion (4/2), not first inversion.

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