When a chord tone other than the root is in the bass, how do we name the inversion and figure it?
Topic 3.2 Triad Inversions and Figures: identify root position, first inversion and second inversion triads, and label them with figured-bass symbols (no figure, 6, and 6/4).
A focused answer to AP Music Theory Topic 3.2, covering triad inversions (root position, first inversion, second inversion) named by the chord tone in the bass, the figured-bass symbols (no figure, 6, 6/4) and how figures measure intervals above the bass, with a worked inversion.
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What this topic is asking
The College Board (Topic 3.2) wants you to recognize a triad's inversion from the chord tone in the bass and to label it with the correct figured-bass symbol. A triad has three notes, so there are three possible bass notes and three positions: root position, first inversion and second inversion.
Inversions are named by the bass
This is why you read inversions from the bottom of the chord up, not from the top. A C major triad voiced with E at the bottom is in first inversion whether the upper notes are C and G, G and C, or doubled in octaves: the bass note E (the third) is all that matters.
Figured bass
The figures are not the chord's name; they are a shorthand for what lies above the bass. In first inversion the bass is the third, so the root sits a sixth above it and the fifth a third above it, giving the figures 6 and 3, abbreviated to just 6. In second inversion the bass is the fifth, so the root is a fourth above it and the third a sixth above it, giving the figures 6 and 4, written 6/4.
Why inversion matters
The central idea is that inverting a chord keeps its identity but changes its stability and its bass line. A root-position triad is the most stable, with the root anchoring the chord; first inversion is lighter and smoother, often used to give the bass a more melodic, stepwise line; second inversion is the least stable because the fourth above the bass behaves like a dissonance that wants to resolve, which is why the 6/4 chord is restricted to a few specific uses later in the course. Recognizing inversion by ear and on the page lets you hear how composers shape a bass line and control tension, and it is essential for Roman numeral analysis, where the figure is attached to the numeral (for example I6 or V6/4) to show both the chord and its position.
Reading an inversion
To find the inversion, identify the chord and its root, then look at the bass note. If the bass is the root, it is root position. If the bass is the third, it is first inversion (6). If the bass is the fifth, it is second inversion (6/4). Then confirm by measuring the intervals from the bass up to the other two chord tones.
Try this
Q1. Which chord tone is in the bass of a first-inversion triad, and what is its figure? [1 point]
- Cue. The third is in the bass; the figure is 6.
Q2. A D minor triad has A in the bass. Name the inversion and figure. [2 points]
- Cue. A is the fifth of D minor (D, F, A), so the chord is in second inversion, figured 6/4.
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 C major triad has E in the bass and C and G in the upper voices. What is the inversion and figure? (A) root position, no figure (B) first inversion, 6 (C) second inversion, 6/4 (D) first inversion, 6/4Show worked answer →
The correct answer is (B) first inversion, 6.
When the third of the triad (here E, the third of a C major chord) is in the bass, the chord is in first inversion, figured 6. The 6 comes from the intervals above the bass: a sixth (E up to C) and a third (E up to G), abbreviated to just 6.
(A) root position has the root C in the bass and no figure. (C) second inversion has the fifth G in the bass, figured 6/4. (D) wrongly pairs first inversion with the 6/4 figure. The trap is naming the inversion from the top note instead of the bass note: the inversion is always decided by which chord tone is lowest.
AP 2023 (style)2 marksSection II (free response, notation). Notate a G major triad in second inversion, name the pitch in the bass, and give the figured-bass symbol.Show worked answer →
A 2-point inversion question.
(1 point) A G major triad is G, B, D. In second inversion the fifth, D, is in the bass, with G and B above it, so the bass note is D.
(1 point) The figured-bass symbol is 6/4, because above the bass D there is a sixth (D up to B) and a fourth (D up to G).
Markers reward placing the fifth (D) in the bass and the correct 6/4 figure. A common error is putting the third (B) in the bass, which would be first inversion (6), not second inversion.
Related dot points
- Topic 3.1 Triads: build a triad as three pitches stacked in thirds (root, third, fifth), and identify its quality as major, minor, diminished or augmented.
A focused answer to AP Music Theory Topic 3.1, covering the triad as stacked thirds (root, third, fifth), the four triad qualities (major, minor, diminished, augmented), how the third and fifth above the root define each quality, and the diatonic triads of a key, with a worked build.
- 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.
- Topic 3.5 Roman Numerals and SATB: label diatonic chords with Roman numerals showing root and quality, and arrange chord tones in the SATB four-voice texture.
A focused answer to AP Music Theory Topic 3.5, covering Roman numeral analysis (case shows quality, figures show inversion), the diatonic numerals of major and minor keys, the SATB four-voice layout and ranges, and how to spell a chord across four voices, with a worked analysis.
- Topic 3.3 Seventh Chords: build a seventh chord by adding a seventh above the root, and identify its quality (major, dominant, minor, half-diminished, fully diminished).
A focused answer to AP Music Theory Topic 3.3, covering the seventh chord as a triad plus a seventh above the root, the five common qualities (major, dominant or major-minor, minor, half-diminished, fully diminished), how the triad and the seventh combine, and the diatonic sevenths of a key, with a worked build.
- Topic 1.1 Pitch and Pitch Notation: identify and notate pitches using the staff, clefs, ledger lines, octave designations, and accidentals.
A focused answer to AP Music Theory Topic 1.1, covering the staff, treble and bass clefs, the grand staff, ledger lines, octave register, enharmonic spellings and accidentals, with a worked pitch-reading example.
Sources & how we know this
- AP Music Theory Course and Exam Description — College Board (2024)