Seventh chords

A seventh chord is a triad with a fourth note added a third above the fifth — that is, a seventh above the root. It sits at the centre of harmonic life from the late Baroque onwards: the engine of every authentic cadence, the staple of every jazz tune, and one of the most expressive resources Romantic composers had at their disposal. Once the ear is trained to hear seventh-chord qualities, three centuries of repertoire become legible at a new level of detail.

Five qualities matter in practice: dominant seventh, major seventh, minor seventh, half-diminished seventh, and fully diminished seventh. Each combines a triad quality with a seventh quality in a specific way, and each has a characteristic role in tonal grammar. Learning to identify all five by ear and on the page is a one-month project with daily drills, and it returns dividends for the rest of your musical life.

Dominant 7      G — B — D — F     major triad + minor 7
Major 7         C — E — G — B     major triad + major 7
Minor 7         D — F — A — C     minor triad + minor 7
Half-dim 7      B — D — F — A     diminished triad + minor 7  (ø7)
Fully-dim 7     B — D — F — A♭    diminished triad + diminished 7  (°7)

The dominant seventh (G-B-D-F in C major) is the most important. It contains a tritone between the third and seventh — B and F — that drives the chord toward resolution. Sound a G7 and the ear is already pulling toward C major before the next chord arrives. The dominant seventh is what makes the perfect authentic cadence feel inevitable, and it is the chord that closes the great majority of phrases in tonal music.

The major seventh (C-E-G-B) sounds lush, modern, and slightly suspended. It is the colour of bossa nova, of Joni Mitchell, of cocktail-jazz piano. Unlike the dominant seventh it does not push to resolve; it sits, glows, and is content to be looked at. Composers from Debussy onwards used major seventh chords as resting points rather than as transitional ones — a shift in role that opened a new musical register.

The minor seventh (D-F-A-C) is the workhorse of jazz harmony. The ii chord in a ii-V-I cadence is almost always a minor seventh; the third chord of a thousand jazz tunes is a minor seventh on the sixth scale degree. It is gentle, slightly melancholy, and stable enough to live with for several bars before moving on.

The half-diminished seventh (B-D-F-A in C major) sits on the seventh scale degree and acts as a substitute for the dominant. It contains the same tritone as the dominant seventh — the diabolus in musica that drives resolution — but voiced more softly. Composers from Wagner onwards used the half-diminished as a Tristan colour, and modern jazz uses it everywhere as a pre-dominant.

The fully diminished seventh (B-D-F-A-flat) stacks three minor thirds and divides the octave into four equal parts. Because it is symmetrical, every inversion sounds like another root position, and the chord can resolve in four different directions depending on which note is heard as the leading tone. Composers exploit this ambiguity for sudden modulations — Mozart, Beethoven, and Schubert all use diminished sevenths as pivot chords for distant key changes.

Inside a V7 to I cadence the third (B in G7) rises to the tonic (C) and the seventh (F) falls to the third (E). The bass moves from G to C — root position to root position — while the inner voices move by step. This is the canonical resolution pattern, and it underwrites the perfect authentic cadence in tonal music. The same logic applies to V7 to vi (the deceptive cadence) with the bass moving up to vi instead.

• V7 → I — tritone resolves outward to the tonic chord.
• ii7 → V7 — root drops a fifth, smooth voice leading.
• ø7 → V7 → I — the soft cousin of the dominant chain.
• °7 → I (in a different key) — symmetric pivot for modulation.

Seventh chords have four notes, and so they have four positions: root, first inversion, second inversion, third inversion. Figured-bass shorthand uses 7 for root position, 6/5 for first inversion, 4/3 for second inversion, and 4/2 (or just 2) for third inversion. The third inversion — the seventh in the bass — is the most striking and the most fragile; it must resolve immediately because the bass is dissonant against the root.

Root position:   G — B — D — F   figured 7
1st inversion:   B — D — F — G   figured 6/5
2nd inversion:   D — F — G — B   figured 4/3
3rd inversion:   F — G — B — D   figured 4/2

Jazz pianists rarely play seventh chords as four-note stacks. Shell voicings keep the third and seventh in the right hand, the root and fifth in the left. Rootless voicings drop the root entirely (the bass player has it) and add ninths, elevenths, or thirteenths in the gaps. The same Cmaj7 might be played as E-G-B-D or as B-D-E-G — both correct, both very different sounds. Voicing is the craft that distinguishes a beginner from an experienced jazz pianist.

Bach and Handel use the dominant seventh constantly; the major seventh is rare in their work because it sounds too modern for Baroque ears. Mozart uses dominant and diminished sevenths heavily, leaning on the diminished's ambiguity for surprise modulations. Schubert opens the door to the half-diminished. Wagner makes the half-diminished a structural sound.

Debussy and Ravel make the major seventh and the dominant ninth into resting points. Bill Evans and Herbie Hancock blow that open into the chord vocabulary jazz still uses today.