Seventh chords
A major chord with a fourth note added, the minor seventh. It creates tension that pulls toward the next chord: it’s the engine of the blues.
What it is
The seventh chord, or dominant seventh, takes a major chord and adds the minor seventh, 10 half steps above the root. Its formula is 1, 3, 5, ♭7.
In G, that gives you G, B, D, F. It’s written with a 7 after the letter: G7. Careful: a 7 on its own doesn’t mean “major 7,” which is a different chord.
The sound: tension that wants to resolve
Play G7, then C: your ear hears a question, then the answer. A seventh chord “pulls” toward the chord a fourth above it: G7 to C, D7 to G, E7 to A. It’s the strongest chord move in tonal music.
In the blues
The blues breaks the rule: it uses seventh chords on every degree, without trying to resolve them. A blues in A goes through A7, D7 and E7: that constant tension is what gives the blues its color.
Shapes to know
Six seventh chords can be played in open position: C7, D7, E7, G7, A7 and B7. Several are easier than the matching major chord: E7 and A7 take one finger fewer than E and A.
All 12 seventh chords
Click a diagram to hear it, or the name to open its full page (every position, tab).