Seventh Chords Theory: Construction, Shapes, and Usage

A seventh chord is a four-note chord built by stacking a third on top of a triad, giving you root, third, fifth, and seventh. The most common is the dominant 7th (e.g., G7 = G–B–D–F), which adds a minor seventh to a major triad. Seventh chords are the foundation of jazz, blues, and soul harmony and add color and tension that plain triads cannot.

The five essential seventh qualities are: dominant 7th (dom7, formula 0-4-7-10), major 7th (maj7, 0-4-7-11), minor 7th (m7, 0-3-7-10), half-diminished (m7♭5, 0-3-6-10), and fully diminished 7th (dim7, 0-3-6-9). Each formula lists the semitone distance of each note from the root. Once you know the five formulas you can build any seventh chord from any starting note.

Both start from a major triad (root, major third, perfect fifth). The dominant 7th adds a minor seventh (10 semitones from the root) — G7 is G–B–D–F, which sounds bluesy and wants to resolve. The major 7th adds a major seventh (11 semitones) — Gmaj7 is G–B–D–F♯, which sounds smooth, bright, and jazzy with no urge to resolve. One semitone in the seventh changes the entire character.

Dominant 7ths define the blues and appear at the V chord in jazz ii–V–I progressions. Major 7ths are the signature sound of jazz and neo-soul. Minor 7ths are everywhere in funk, R&B, and as the ii chord in jazz. Half-diminished (m7♭5) chords drive minor-key ii–V–i progressions. Fully diminished 7th chords create tension for dramatic transitions and resolution by stepping down a semitone in any direction.