Chord Inversion¶
The classification of a rooted triad or seventh chord by which of its chord members occupies the sounding bass.
Core Idea¶
Chord inversion describes which member of an analyzed chord is the lowest sounding note. In a triad, root in the bass is root position, third in the bass is first inversion, and fifth in the bass is second inversion. A seventh chord adds third inversion, with its seventh in the bass. The chord's root and quality stay the same under the chosen analysis: F/A remains F major, not an A-root chord.[triads][figures]
Scope of Application¶
The classification is used in lead sheets, Roman-numeral analysis, figured bass, arranging and performance whenever a rooted triad or seventh chord is identifiable. Puget Sound's §6.3 slash-chord table gives F/A as a first-inversion triad, with 6/3 intervals above the bass; its §16.6 seventh-chord exercise gives G7/F as a third-inversion chord labeled V4/2 in C. Style-specific questions such as whether a 6/4 chord is cadential, passing, pedal or melodic-bass require more context than the inversion label alone.[triads][practice][figures][sixfour]
Clarity¶
Separate root (the chord's organizing pitch), bass (the lowest sounding pitch), inversion (that bass pitch's role as root, third, fifth or seventh), and voicing (the placement of all parts). Moving upper notes without changing the bass need not change inversion. A slash symbol by itself is not proof: C/F♯ has a bass note outside the C-major triad and therefore is not an ordinary inversion of C.[^triads]
Manages Complexity¶
Many octave placements and upper-voice spacings of one chord reduce to a few root–bass classes: three positions for a triad and four for a seventh chord, counting root position. Figured-bass numerals compress the intervals above the bass. The shorthand does not reveal every doubled note, voice-leading choice or harmonic function, so it should supplement rather than replace analysis.[^figures]
Abstract Reasoning¶
Identify the chord's root and members first, then locate the actual lowest sounding pitch. If it is a chord member, map root/third/fifth/seventh to root/first/second/third position. If it is not a chord member, do not force an inversion label. Only after that classification infer any notation or style-specific function. This order prevents mistaking an altered bass for a new root or treating all second-inversion chords as the same kind of cadence.[triads][sixfour]
Knowledge Transfer¶
The root–bass test transfers literally between lead-sheet symbols, figured bass and Roman-numeral analysis despite their different notations. Common-practice expectations about a cadential 6/4 do not automatically transfer to every style.
[^triads]: Robert Hutchinson, Music Theory for the 21st-Century Classroom, §6.3 “Inverted Triads”, University of Puget Sound. [^figures]: Chelsey Hamm, “Figured Bass,” Open Music Theory, Triadic and Seventh Chord Figures. [^practice]: Hutchinson, §16.6 “Practice Exercises”, seventh-chord answer 2 containing G7/F; F/A is in §6.3, cited separately. [^sixfour]: Hutchinson, §16.4 “Other Occurrences of Six-Four Chords”, classical-style use cases.
Relationships to Other Abstractions¶
Current abstraction Chord Inversion Domain-specific
Parents (1) — more general patterns this builds on
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Chord Inversion presupposes Root (chord) Domain-specific
Classifying chord inversion presupposes a stable analyzed chord root against which the sounding bass member can be identified.
Hierarchy path (1) — routes to 1 parentless root
- Chord Inversion → Root (chord) → Reference-Point Dependence → Comparison → Self Checking
Neighborhood in Abstraction Space¶
Chord Inversion sits in a sparse region of the domain-specific corpus (84th percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.
Family — Tonal Harmony & Key Structure (14 abstractions)
Nearest neighbors
- Tertian — 0.87
- Diminished Triad — 0.84
- Basso Continuo — 0.82
- Pitch Space — 0.81
- Tonality — 0.81
Computed from structural-signature embeddings · 2026-10-08