A chord that is already leaning toward the door.
The Chord
The dominant seventh is a major triad with a minor seventh stacked on top — a major third, a minor third, then another minor third. On C the notes are C, E, G, B♭. That flattened seventh is the difference between a chord that sits still and a chord that moves. Inside the dominant seventh live two notes a tritone apart — the third and the seventh — and that interval is the most restless in tonal music, the coiled spring at the centre of the whole system.
The tritone between E and B♭ wants to collapse inward: the E rising, the B♭ falling, each resolving by a half step into the notes of a tonic chord a fifth below. This is the engine of Western harmony. The dominant seventh is not a place to rest; it is a chord that exists in order to go somewhere.
Structure
| Attribute | Value |
|---|---|
| Formula | 1 3 5 ♭7 |
| Notes (on C) | C E G B♭ |
| Symbol | C7 |
| Quality | The engine of tension that wants to resolve |
Character
The dominant seventh is tension with a grin. It has the brightness of a major triad but a gritty, unresolved edge that can read as bluesy swagger or urgent forward drive. Held on its own it sounds raw and alive; in a progression it sounds like momentum. The blues loves it so much that it builds entire songs from dominant chords that never fully resolve.
In Practice
As the V7 of any key, the dominant seventh powers the strongest cadence in tonal music, pulling home to the tonic. In blues, jazz, funk, and rock it becomes a colour in its own right, used on the I and IV as much as the V. Chains of dominants — the circle-of-fifths motion — drive whole tunes. It is the Major Triad set into motion, and it resolves most naturally toward the tonic of a key in Musical Keys.