Seventh chords, explained
Add one more third on top of a triad and you get a seventh chord — the sound that separates blues, jazz and gospel from plain triadic pop. There are five flavors worth knowing, and they all appear in real songs constantly.
How seventh chords are built
A triad stacks two thirds: root, third, fifth. A seventh chord stacks one more, adding the note a seventh above the root. Which kind of triad and which kind of seventh you combine determines the flavor — five combinations cover almost everything you will meet.
Dominant seventh (C7): the engine of motion
C7 = C–E–G–B♭: a major triad plus a minor seventh. The major third and minor seventh form a tritone inside the chord, and that interval demands resolution. A dominant seventh built on the fifth degree of a key (G7 in C major) pulls almost irresistibly back to the tonic.
Blues bends this rule beautifully: a 12-bar blues plays dominant sevenths on every chord — I7, IV7, V7 — and lives happily inside the tension. If a song says just "C7", this is the chord it means.
Major seventh (Cmaj7): the soft landing
Cmaj7 = C–E–G–B: a major triad plus a major seventh. The B sits one half-step below the root's octave, adding a gentle, settled glow instead of tension. It is the default "pretty" chord of bossa nova, neo-soul and jazz ballads. Play C, then Cmaj7 — same brightness, more air.
Minor seventh (Cm7): the workhorse
Cm7 = C–E♭–G–B♭: minor triad plus minor seventh. Softer than a plain minor triad, it is the most common chord in soul, funk and jazz. In a major key, the ii chord (Dm7 in C) is a minor seventh — the start of the ubiquitous ii–V–I: Dm7 → G7 → Cmaj7.
The diminished pair: dim7 and m7♭5
Cdim7 (C–E♭–G♭–B♭♭) stacks minor thirds all the way — fully symmetric, maximally tense, perfect as a chromatic passing chord. Cm7♭5 (C–E♭–G♭–B♭), the half-diminished chord, keeps a minor seventh on top; it is the standard ii chord in minor keys (Dm7♭5 → G7 → Cm).
A useful ear check: dim7 sounds like a silent-film cliffhanger; m7♭5 sounds like the first chord of "Autumn Leaves"' minor turnaround — dark but composed.
Hearing and using the differences
Play these four bars: Dm7 | G7 | Cmaj7 | Cmaj7. That ii–V–I contains three of the five types doing their natural jobs: the m7 sets up, the dominant 7 pushes, the maj7 lands. Then swap Cmaj7 for C7 and hear the landing turn restless — that single note (B vs B♭) is the whole story of seventh chords.
Keep exploring
Frequently asked questions
What is the difference between C7 and Cmaj7?
The seventh. C7 has a minor seventh (B♭) and sounds tense; Cmaj7 has a major seventh (B) and sounds settled. They are not interchangeable.
Why is it called a dominant seventh?
Because it naturally occurs on the fifth scale degree — the "dominant" — of a major key. G7 is the dominant seventh in C major and resolves to C.
What does m7♭5 mean?
Minor seventh flat five, also called half-diminished: a diminished triad with a minor seventh (C–E♭–G♭–B♭). It is the standard ii chord in minor keys.
Which seventh chord should I learn first?
The dominant seventh (G7, C7, D7) — it appears in more songs than any other, and the ii–V–I pattern that runs through jazz and pop is built around it.
