Seventh Chord Inversions and Figures - AP Music Theory Study Guide

Getting Started

Building upon your knowledge of triads and their inversions, this section introduces seventh chords. By adding a fourth note to a triad, we create a richer, more complex sonority that allows for an additional inversion, expanding the possibilities for creating smooth bass lines and nuanced harmonic progressions.

What You Should Be Able to Do

• Identify the root, quality, and inversion of any seventh chord from a musical score.

• Provide the correct Roman and Arabic numerals for seventh chords in major and minor keys.

• Aurally distinguish between the different inversions of a seventh chord based on the sound of its bass note.

• Analyze a harmonic progression by identifying the function of chords, including seventh chords in all inversions.

Key Concepts & Analysis

The analysis of seventh chords integrates Roman numerals, which denote the root and quality of a chord, with figured bass, which indicates its inversion. Understanding how these elements work together is essential for describing the harmonic function of chords within a musical phrase.

Seventh Chords and Figured Bass

A seventh chord is a four-note chord built of a root, a third, a fifth, and a seventh. Like triads, seventh chords can be inverted. An inversion places a chord member other than the root in the bass. Because seventh chords have four notes, they have four possible positions: root position and three inversions.

Figured Bass is a system of Arabic numerals written after a Roman numeral to specify the inversion. The numbers represent the simple intervals formed by the upper notes with the bass note.

Roman Numeral Analysis and Harmonic Function

Roman Numeral Analysis is the method of labeling chords to indicate the scale degree of their root, their quality (major, minor, etc.), and their inversion. The Roman numeral itself conveys the root and quality, while the figured bass conveys the inversion.

A chord's harmonic function describes its role within a key, typically categorized as Tonic (stability), Dominant (tension), or Predominant (transition to dominant). While inversions can alter the melodic shape of the bass line and the relative stability of a chord, they do not change its fundamental function.

• Dominant Function: The most common seventh chord is the dominant seventh, built on the fifth scale degree (V7). In all its inversions (V7, V6/5, V4/3, V4/2), it retains its strong pull toward the tonic. The third inversion, V4/2, is particularly potent, as the dissonant chordal seventh is in the bass, creating a strong need for resolution.

• Predominant Function: Seventh chords built on the supertonic (ii7) and subdominant (IV7) serve a predominant function, preparing the arrival of the dominant. The supertonic seventh in first inversion (ii6/5) is especially common, creating a smooth bass motion of ^4 to ^5 when moving to a V chord.

• Tonic Function: Seventh chords can be built on the tonic (Imaj7 or i7), but they are less common in foundational harmonic progressions. They are often used for harmonic color rather than functional drive.

The primary analytical task is to identify the root of the chord to determine its Roman numeral, then identify which chord member is in the bass to determine the correct figured bass symbol. For example, in C major, the notes (from bottom up) F, G, B, D form a V4/2 chord. The root is G (^5, so V), and the seventh of the chord (F) is in the bass, indicating third inversion (4/2).

Data & Organization Tools

This table shows the diatonic seventh chords in a major key, their qualities, and their most common harmonic functions. The same functions apply when the chords are inverted.

Evidence Bank

• Root Position (7): The most stable position of a seventh chord, with the root in the bass. Labeled with a 7, as in V7.

• First Inversion (6/5): The chord with its third in the bass. Often used to create smoother bass lines, as in a ii6/5 moving to V.

• Second Inversion (4/3): The chord with its fifth in the bass. This inversion is often used as a passing or neighboring chord, as in I - V4/3 - I6.

• Third Inversion (4/2): The chord with its seventh in the bass. This is the most unstable inversion and is unique to seventh chords. It creates significant tension and is almost exclusively used for dominant-function chords (V4/2).

• Chordal Seventh: The note that is a seventh above the root of the chord. This note is a dissonance that typically resolves down by step.

• Dominant Seventh Chord (V7): The seventh chord built on the fifth scale degree. Its primary function is to create tension that resolves to the tonic (I or i).

• Supertonic Seventh Chord (ii7): The seventh chord built on the second scale degree. Its primary function is predominant, preparing the dominant.

Skill Snapshots

Functional

• I - ii6/5 - V7 - I: A standard progression where the first-inversion ii chord creates a smooth bass line (^1 - ^4 - ^5 - ^1) leading to the dominant.

• I - V4/3 - I6: Here, the second-inversion dominant acts as a passing chord, connecting the root-position tonic to its first inversion. The bass line moves stepwise: ^1 - ^2 - ^3.

• I6 - V4/2 - I: The third-inversion dominant creates intense drive to the tonic. The bass note (^4) resolves down to ^3, while the leading tone within the chord resolves up to ^1.

Voice-Leading

• Rule: The chordal seventh is a dissonance that resolves down by step. Effect: In a V4/2 - I progression, the bass note itself is the chordal seventh and must resolve down by step.

• Rule: The leading tone (^7) resolves up to the tonic (^1). Effect: In a V6/5 chord, the leading tone is in the bass, creating a powerful melodic pull upwards to the root of the tonic chord.

• Rule: Inversions create melodic bass lines. Effect: Using I - IV - V - I creates a bass line with leaps (^1 - ^4 - ^5 - ^1). Using I - IV6/5 - V - I creates a smoother bass line (^1 - ^6 - ^5 - ^1).

Form

• Baseline Phrase: A phrase ending with ii7 - V7 - I uses root position chords to create a strong, standard authentic cadence.

• Contrasting Phrase: A phrase ending with IV - V4/2 - I uses the unstable third inversion dominant to heighten the tension and sense of arrival at the cadence.

• Continuity: Mid-phrase, a V4/3 can connect two tonic-function chords (e.g., I - V4/3 - I6) without creating the finality of a cadence, thus propelling the music forward.

Common Misconceptions & Clarifications

• Confusing the Bass Note with the Root: The Roman numeral always refers to the scale degree of the chord's root, not the note in the bass. A V6/5 chord in C major has B in the bass, but its root is G, so it is labeled V.

• Mixing Triad and Seventh Chord Figures: A first inversion triad is 6. A first inversion seventh chord is 6/5. The additional figure is necessary to account for the fourth note of the chord.

• Assuming All Seventh Chords are Dominant: While V7 is the most frequently used seventh chord, diatonic seventh chords can be built on any scale degree, each with a distinct quality and function (e.g., ii7 is predominant, Imaj7 is tonic).

• Misidentifying the Root of Inversions: To find the root of an inverted seventh chord, stack the given notes into thirds. The note at the bottom of the stack is the root.

Summary

Seventh chords are four-note sonorities that introduce a chordal seventh and a third inversion. The system of Roman and Arabic numerals allows for precise identification of a seventh chord's root, quality, and inversion. The figures 7, 6/5, 4/3, and 4/2 correspond to root position, first inversion, second inversion, and third inversion, respectively. While inversions are critical for creating melodic bass lines and varying harmonic texture, they do not alter a chord's fundamental harmonic function as Tonic, Predominant, or Dominant. A firm grasp of this analytical system is essential for understanding the structure and grammar of tonal music.