Seventh Chord
A triad plus one more third — the seventh adds direction
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A seventh chord adds one more third to a triad, making four notes: root, third, fifth and seventh. The seventh is unstable and gives the chord a direction — the dominant seventh (major triad plus minor seventh) especially, which almost naturally points to the tonic.
Common types include dominant, major, minor, half-diminished and diminished sevenths. The name depends on both the third and the seventh, so "minor seventh" is not "minor chord plus any seventh". Sevenths can be inverted and stacked further into ninths, elevenths and thirteenths — each layer adds colour and complicates the direction.
Read deeper → Seventh Chord
Sources
- 七和弦的构成与常见类型，参 The New Grove Dictionary of Music and Musicians, "Seventh chord"；本文为原创表述
Used for fact-checking only; all prose is original.