Music chords: triads, sevenths, progressions and cadences
A chord is three or more notes sounding together, usually stacked in thirds. The chords of a key are numbered with Roman numerals, the order in which they follow each other is a progression, and a progression that closes a phrase is a cadence. In this guide, we'll take these four ideas one at a time, and you'll hear each of them.
Triads and seventh chords
Let's start with the building blocks. A triad stacks two thirds on a root, like C, E, G. Whether it's major, minor, diminished or augmented depends on the size of those thirds. Add another third on top, and you get a seventh chord: C, E, G, B♭ is C7, the dominant seventh. You'll find every chord on every root, with keyboard diagrams, in the piano chord chart.
| Quality | Thirds, from the bottom | On C |
|---|---|---|
| Major | major, then minor | C, E, G |
| Minor | minor, then major | C, E♭, G |
| Diminished | minor, then minor | C, E♭, G♭ |
| Augmented | major, then major | C, E, G♯ |
The chords of a key
Now build a triad on each note of the major scale, using only the notes of the scale, and you get seven chords. Uppercase numerals mean major chords, lowercase numerals mean minor chords, and the small circle marks the diminished chord. The pattern is the same in every major key.
Common chord progressions
- I V vi IV gives C, G, A minor, F in C. The verse of “Let It Be” by the Beatles and “Don't Stop Believin'” by Journey both use it.
- I vi IV V is the doo-wop progression of the 1950s, as in “Stand by Me”.
- ii V I is the backbone of jazz harmony: Dm7, G7, Cmaj7 in C.
- The 12-bar blues has four bars of I, two of IV, two of I, then V, IV, I and a turnaround.
US Roman numerals: uppercase = major, lowercase = minor, ° = diminished, ø = half-diminished; 6, 6/4, 6/5, 4/3, 4/2 = inversions; V/V = dominant of the dominant.
The four cadences
| Cadence | Chords | Effect |
|---|---|---|
| Authentic (perfect) | V to I | a full stop |
| Half | ends on V | a comma, a question |
| Plagal | IV to I | the “Amen” at the end of hymns |
| Deceptive | V to vi | a surprise: you expect I and hear a minor chord |
US Roman numerals: uppercase = major, lowercase = minor, ° = diminished, ø = half-diminished; 6, 6/4, 6/5, 4/3, 4/2 = inversions; V/V = dominant of the dominant.
Focus on the last two chords and on the top note. The phrase always starts on the tonic, which sets the key.