3.4 Seventh Chords

Seventh chords are four note chords built by stacking thirds, adding a seventh above the root of a triad. The five qualities you need to recognize are major (MM/M7), dominant or major minor (Mm7), minor (mm/m7), half diminished (ø7), and fully diminished (°7).

Why This Matters for the AP Music Theory Exam

Seventh chords show up across the harmonic side of AP Music Theory. Being able to name a chord's quality from notation and from sound supports harmonic dictation, score analysis, and Roman-numeral labeling. This topic also sets up later work, since the dominant seventh and its resolution are central to functional harmony, voice leading, and cadences in Units 4 and 5. Train your ear to tell these qualities apart inside a progression, not just in isolation, because that is closer to how chords actually behave on the exam.

Key Takeaways

• A seventh chord is four pitches stacked in thirds: root, third, fifth, and seventh.
• The five common qualities are major seventh (MM, M7), dominant/major-minor seventh (Mm7), minor seventh (mm, m7), half-diminished seventh (ø7), and fully-diminished seventh (°7).
• A chord's quality comes from the triad plus the type of seventh above the root.
• The seventh is a chordal dissonance, a note with a natural pull to resolve, usually downward by step.
• In a major key, diatonic seventh chord qualities follow a fixed pattern: I and IV are major sevenths, ii, iii, and vi are minor sevenths, V is a dominant seventh, and viiø7 is half-diminished.
• In minor keys, raising the leading tone changes some qualities, so the dominant-function chords differ from the natural-minor versions.

The Five Seventh Chord Qualities

A seventh chord adds a fourth note a seventh above the root of a triad. The quality depends on two things: the triad underneath and the kind of seventh on top.

• Major seventh (MM, M7): major triad plus a major seventh above the root. Bright, smooth sound.
• Dominant / major-minor seventh (Mm7): major triad plus a minor seventh above the root. This is the chord that drives toward resolution, which is why a major-minor chord acting in dominant function is called a dominant seventh.
• Minor seventh (mm, m7): minor triad plus a minor seventh above the root. Mellow, mild sound.
• Half-diminished seventh (ø7, also called diminished-minor): diminished triad plus a minor seventh above the root.
• Fully-diminished seventh (°7, also called diminished-diminished): diminished triad plus a diminished seventh above the root. The most tense of the five.

One quick way to keep ø7 and °7 straight: both start on a diminished triad, but the half-diminished has a minor seventh while the fully-diminished has a diminished seventh.

Building Seventh Chords from Each Triad

Think of a seventh chord as a triad with one more third stacked on top. The triad sets the base, and the top third decides the seventh quality.

From a major triad (use C-E-G):

• Add a major third on top (B) for a major seventh chord (MM / M7): C-E-G-B.
• Add a minor third on top (B♭) for a major-minor / dominant seventh chord (Mm7): C-E-G-B♭.

From a minor triad (use C-E♭-G):

• Add a minor third on top (B♭) for a minor seventh chord (mm / m7): C-E♭-G-B♭.

From a diminished triad (use B-D-F):

• Add a major third on top (A) for a half-diminished seventh chord (ø7): B-D-F-A.
• Add a minor third on top (A♭) for a fully-diminished seventh chord (°7): B-D-F-A♭.

Why Quality Lines Up in a Major Key

In a major key, the seventh chord built on each scale degree usually matches the quality of its triad, with a couple of important exceptions.

Here is the intuition. Take the upper three notes of a seventh chord (third, fifth, seventh). They form their own triad. If the base triad is major, that upper triad is minor, so the seventh above the root comes out major. If the base triad is minor, the upper triad is major, so the seventh comes out minor.

Two chords break the simple pattern:

• The V chord ends up as a dominant seventh (Mm7), which is where the name "dominant seventh" comes from.
• The vii chord has a diminished triad with a minor seventh on top, so it is half-diminished (viiø7), not fully diminished.

So in C major, the diatonic seventh chords are:

Seventh Chords in Minor Keys

In minor, the qualities are not as uniform because the leading tone is often raised to give the dominant its pull. You raise the seventh scale degree for the dominant-function chords, but not for the tonic or mediant chords.

Using A minor with the raised leading tone (G♯) where it matters:

A few spelling notes that matter for AP:

• The V chord in A minor is E-G♯-B-D. The G♯ is the raised leading tone, and the D is a minor seventh above E, so this is a dominant seventh (Mm7), not a major seventh. Do not call it a major seventh chord; it does not contain a major seventh.
• The vii°7 in A minor is G♯-B-D-F, with its root on the raised seventh scale degree (G♯). Here F is a diminished seventh above G♯, which is what makes the chord fully diminished. The note is spelled F, not E♯, because the chord is stacked in thirds above G♯.
• You usually do not raise the sixth scale degree, since the raised sixth has a melodic role rather than a harmonic one.

Try this check: can you spell a Gø7 (G half-diminished seventh)? Start with the diminished triad G-B♭-D♭, then add a minor seventh, F, on top: G-B♭-D♭-F.

Inversions in Brief

Like triads, seventh chords can appear with a note other than the root in the bass. Because a seventh chord has four notes, it has a third inversion in addition to root position, first, and second inversion.

• Root position: root in the bass
• First inversion: third in the bass
• Second inversion: fifth in the bass
• Third inversion: seventh in the bass

The figured-bass symbols and how to label each inversion are covered fully in 3.5.

How to Use This on the AP Music Theory Exam

Listening and Dictation

Practice telling the five qualities apart by ear, both in isolation and inside a progression. Start by hearing the triad quality, then listen for whether the seventh sounds major, minor, or diminished. The dominant seventh's pull toward resolution is one of the most recognizable cues.

Score Analysis

When you see a four-note chord stacked in thirds, identify the root, then check the triad quality and the seventh above the root. Use that to assign the correct quality label and Roman numeral with its quality symbol (for example, ø7 or °7).

Common Trap

Always confirm whether you are in major or minor and whether the leading tone is raised before labeling a chord in a minor key. The same letter names can spell different qualities depending on accidentals.

Common Misconceptions

• "A dominant seventh has a major seventh because it sits on a major triad." It has a major triad with a minor seventh on top. That is why it is called major-minor (Mm7).
• "Half-diminished and fully-diminished are the same." Both use a diminished triad, but ø7 has a minor seventh and °7 has a diminished seventh. That one note changes the quality and the sound.
• "In minor, the V seventh chord is a major seventh chord." With the raised leading tone, V in minor is a dominant seventh (Mm7), like E-G♯-B-D in A minor. It does not contain a major seventh.
• "The vii°7 in minor is built on the natural seventh degree." Its root is the raised seventh scale degree, such as G♯ in A minor, and the seventh (F) is a diminished seventh above that root.
• "Major-key diatonic seventh chords are all major or minor." The V is a dominant seventh and the vii is half-diminished, so not every chord matches its triad label exactly.
• "The seventh can go anywhere." The seventh is a chordal dissonance with a strong tendency to resolve, usually down by step, which matters a lot once you reach voice leading.

Related AP Music Theory Guides

• 3.1 Triad and Chord Qualities (M, m, d, A)
• 3.2 Diatonic Chords and Roman Numerals
• 3.5 Seventh Chord Inversions and Figures
• 3.3 Chord Inversions and Figures: Introduction to Figured Bass
• Unit 3 Overview: Music Fundamentals III (Triads and Seventh Chords)