Triad
A triad is a chord of three notes stacked in thirds: a root, the third above it and the fifth above it.
What are the four kinds of triad?
The two thirds in the stack decide the kind. Built on C:
| Triad | Notes | Semitones from the root | Symbol |
|---|---|---|---|
| Major | C–E–G | 4, 7 | C |
| Minor | C–E♭–G | 3, 7 | Cm |
| Diminished | C–E♭–G♭ | 3, 6 | Cdim or C° |
| Augmented | C–E–G♯ | 4, 8 | Caug or C+ |
Major and minor have a perfect fifth and differ only in the third, by one semitone. Diminished and augmented change the fifth as well.
Every major key contains seven triads, one on each degree. In C major: C, Dm, Em, F, G, Am and Bdim.
How does a triad sound?
The third gives a triad its colour. A major third (4 semitones) sounds bright and open; a minor third (3) sounds darker and more inward. The perfect fifth adds weight and stability without changing that colour.
Diminished and augmented triads have no perfect fifth, and both sound unstable: diminished squeezed and anxious, augmented stretched and suspended. Neither sounds like a place to stop.
To recognise a triad by ear, find the root first, then sing the note a third above it and ask whether it is the bright one or the dark one.
Is any three-note chord a triad?
No. A triad is built in thirds. C–D–E has three notes but stacks seconds, so it is a cluster, not a triad. A guitar “power chord” (C–G, often with C doubled on top) has no third at all, so it is neither major nor minor.
The order of the notes, on the other hand, does not matter. E–G–C is still a C major triad, with E in the bass: an inversion, not a different chord.
Try it: Chord Quality by Ear plays a triad and asks which of the four kinds it is. Building Chords has you build them from any root.