Seventh Chords

Adding a fourth note (the seventh degree above the root) to a triad creates a seventh chord. Seventh chords are the standard harmonic unit in jazz and much of modern music.

The Five Common Seventh Chord Types

Major 7th (Maj7): 1-3-5-7. A major triad + major 7th. Sound: lush, sophisticated, dreamy. Used on I and IV in major keys. Example: Cmaj7 = C-E-G-B. Minor 7th (m7): 1-b3-5-b7. A minor triad + minor 7th. Sound: warm, mellow, nostalgic. Used on ii, iii, vi in major keys. Example: Cm7 = C-Eb-G-Bb. Dominant 7th (7): 1-3-5-b7. A major triad + minor 7th. Sound: bluesy, tense, wants to resolve. Used on V. The tension between the major 3rd and minor 7th (a tritone) is what makes dominant chords pull toward resolution. Example: C7 = C-E-G-Bb. Minor 7 flat 5 (m7b5, half-diminished): 1-b3-b5-b7. A diminished triad + minor 7th. Sound: dark, unresolved, searching. Used on vii in major and ii in minor keys. Example: Cm7b5 = C-Eb-Gb-Bb. Diminished 7th (dim7): 1-b3-b5-bb7. A diminished triad + diminished 7th. Sound: symmetrical tension, every note equidistant. Four notes each a minor 3rd apart, so there are only three unique diminished 7th chords. Example: Cdim7 = C-Eb-Gb-Bbb(A).

Diatonic Seventh Chords in Major

Why Seventh Chords Matter

Seventh chords add color and harmonic specificity. Where a C major triad is ambiguous (is it I or V?), a Cmaj7 is clearly tonic and a C7 is clearly dominant. The added note narrows the chord's function, making harmonic progressions clearer and more expressive.