Harmony
The seven chords you get by building a triad on each note of a major scale — and the pattern of qualities that never changes.
Build a triad on each scale degree by stacking every other note. Degree 1 gives C–E–G, a C major chord. Degree 2 gives D–F–A, a D minor chord. Keep going up the scale and you get seven chords — three major, three minor, one diminished.
| Numeral | Quality | Key of C | Key of G |
|---|---|---|---|
| I | major | C | G |
| ii | minor | Dm | Am |
| iii | minor | Em | Bm |
| IV | major | F | C |
| V | major | G | D |
| vi | minor | Am | Em |
| vii° | diminished | B° | F♯° |
The order never changes. Learn it once and it works in every major key.
Stack one more third on top of each triad and you get its seventh chord. Four qualities come out of the scale: major 7th on I and IV, minor 7th on ii, iii and vi, a dominant 7th on V, and a half-diminished 7th (m7♭5) on vii°.
The numerals are movable. Spell any major scale, stack the thirds, and you have that key’s seven chords — same qualities, same order, every time.