Diatonic chords are the seven chords built from the notes of a key, one on each degree of the scale. In C major they are C, Dm, Em, F, G, Am and Bdim, and they are the chords that belong to the key, with no notes from outside the scale.
What are diatonic chords?
Diatonic chords are the seven chords built from the notes of a key, one on each degree of the scale, using only the notes of that scale. In C major the diatonic chords are C, Dm, Em, F, G, Am and Bdim, in the order I, ii, iii, IV, V, vi, vii. They are the chords that belong to the key, with no notes from outside the scale, and they are the chords that most songs are built from, because they sound at home together. The diatonic chords matter because they are the harmonic vocabulary of a key. A song in C major will use mostly diatonic chords, with the occasional non-diatonic chord, such as a secondary dominant or a borrowed chord, added for colour. The pattern is the same in every major key: three major chords, three minor chords and one diminished chord, in the order I, ii, iii, IV, V, vi, vii. In a minor key the pattern is different: three minor chords, three major chords and one diminished chord, in the order i, ii, iii, iv, v, VI, VII, because the natural minor scale has a different arrangement of intervals. The key of C major lists the diatonic chords of C major, and the key of A minor lists the diatonic chords of A minor.
How diatonic chords are built
Diatonic chords are built by stacking 3rds on each degree of the scale, using only the notes of the scale. In C major, the scale is C, D, E, F, G, A, B, and the chord on C is C, E, G, the 1st, 3rd and 5th degrees. The chord on D is D, F, A, the 2nd, 4th and 6th degrees. The chord on E is E, G, B, the 3rd, 5th and 7th degrees. The pattern continues around the scale, and each chord uses every other note, which is why the chords are called diatonic: they are built from the scale itself, with no outside notes. The qualities of the diatonic chords follow from the intervals of the scale. In a major key the I, IV and V chords are major, because their 3rds are major, the ii, iii and vi chords are minor, because their 3rds are minor, and the vii chord is diminished, because its 3rd is minor and its 5th is diminished. In a natural minor key the i, iv and v chords are minor, the III, VI and VII chords are major, and the ii chord is diminished. The C major scale shows the notes the chords are built from, and the chord finder builds any diatonic chord from any root.
Worked example — the diatonic chords of G major. The G major scale is G, A, B, C, D, E, F#, and the chords are built by stacking 3rds on each degree. On G, the notes are G, B, D, a major triad, the I chord. On A, the notes are A, C, E, a minor triad, the ii chord. On B, the notes are B, D, F#, a minor triad, the iii chord. On C, the notes are C, E, G, a major triad, the IV chord. On D, the notes are D, F#, A, a major triad, the V chord. On E, the notes are E, G, B, a minor triad, the vi chord. On F#, the notes are F#, A, C, a diminished triad, the vii chord. The key of G major lists the same seven chords, and the G major guitar chord is the I chord.
How to practise diatonic chords
Practise diatonic chords by building them from the scale, not by memorising chord lists, so the skill transfers to every key.
- Pick a key, write out its scale, and build the triad on each of its seven degrees by stacking 3rds, naming the quality of each chord as you go.
- Play the diatonic chords of the key of C major in order, I, ii, iii, IV, V, vi, vii, and listen for the three major, three minor and one diminished chords.
- Play the diatonic chords of the key of G major and the key of D major, and check that the pattern of qualities is the same in every major key.
- Play the I–V–vi–IV progression in C major and notice that all four chords are diatonic, which is why the progression sounds so natural.
- Use the chord finder to build the diatonic chords of any key, and check your answers against the key page.
Common mistakes
- Using a chord from outside the key — A chord that contains a note from outside the scale is not diatonic, and it will sound like a visitor, not a resident. Non-diatonic chords are useful for colour, but they should be used deliberately, not by accident.
- Forgetting the diminished chord — Every major key has one diminished chord, on the 7th degree, and every minor key has one diminished chord, on the 2nd degree. Forgetting it leaves a gap in the key, and the vii chord is the one that pulls most strongly back to the tonic.
- Thinking the V chord is minor in a major key — The V chord of a major key is major, because its 3rd is major. In C major the V chord is G major, not G minor, and playing it as minor will clash with the key.
Quick reference
This table lists the diatonic chords of three major keys side by side, so you can see that the pattern of qualities is identical in every major key, even though the notes are different. In every column the I, IV and V chords are major, the ii, iii and vi chords are minor, and the vii chord is diminished, which is the pattern to memorise.
| Degree | C major | G major | D major |
|---|---|---|---|
| I | C | G | D |
| ii | Dm | Am | Em |
| iii | Em | Bm | F#m |
| IV | F | C | G |
| V | G | D | A |
| vi | Am | Em | Bm |
| vii° | Bdim | F#dim | C#dim |
Work through the table by building the diatonic chords of A major yourself, using the same pattern, and checking that you get A, Bm, C#m, D, E, F#m and G#dim. When you can build the diatonic chords of any major key without looking, you can play the harmony of most songs in that key.
Frequently asked questions
What are diatonic chords?
Diatonic chords are the seven chords built from the notes of a key, one on each degree of the scale. In C major they are C, Dm, Em, F, G, Am and Bdim, and they are the chords that belong to the key, with no notes from outside the scale.
How many diatonic chords are in a key?
Seven, one on each degree of the scale. In a major key they are I, ii, iii, IV, V, vi and vii, and in a natural minor key they are i, ii, III, iv, v, VI and VII, with the same seven chords in a different order.
What is the pattern of diatonic chords in a major key?
Three major chords, three minor chords and one diminished chord, in the order I, ii, iii, IV, V, vi, vii. The I, IV and V chords are major, the ii, iii and vi chords are minor, and the vii chord is diminished.
Can a song use chords from outside the key?
Yes, and many do. Non-diatonic chords such as secondary dominants and borrowed chords add colour and drama, but they are used deliberately, as visitors, while the diatonic chords are the residents that the song returns to.
Why are diatonic chords important?
Because they are the harmonic vocabulary of a key, and most songs are built from them. If you know the diatonic chords of a key, you can play the harmony of most songs in that key, transpose progressions, and work out the key of a song from its chords.