Diatonic chords are the chords built naturally from the notes of a scale — no sharps or flats added outside the key. Every major scale produces seven diatonic chords, and understanding which ones are major, minor, and diminished is how you start writing progressions that feel intentional rather than accidental.
How Diatonic Chords Are Built
To build a diatonic chord on a given scale degree, you stack thirds using only the notes in the scale. Stack the root, then skip a note (add the third), skip another (add the fifth). Every note you add must come from the scale itself.
Diatonic Chords in C Major
| Degree | Roman Numeral | Chord | Quality |
|---|---|---|---|
| 1 | I | C major | Major |
| 2 | ii | D minor | Minor |
| 3 | iii | E minor | Minor |
| 4 | IV | F major | Major |
| 5 | V | G major | Major |
| 6 | vi | A minor | Minor |
| 7 | vii° | B diminished | Diminished |
The pattern — Major, minor, minor, Major, Major, minor, diminished — is the same in every major key. Only the chord names change.
Roman Numeral Notation
Roman numerals are used to describe chord functions independent of key. Uppercase = major, lowercase = minor, ° = diminished. This lets you describe a progression once and apply it anywhere:
- I – V – vi – IV in C major: C – G – Am – F
- I – V – vi – IV in G major: G – D – Em – C
- Same progression, different key.
The Three Most Important Chords
Three chords carry the most harmonic weight in any major key:
- I (tonic) — home base. Feels resolved and stable.
- IV (subdominant) — moves away from home. Softer tension.
- V (dominant) — strong tension that wants to resolve back to I.
Hundreds of thousands of songs have been written using only I, IV, and V. The 12-bar blues is the most famous example.
The vi Chord
The vi chord (relative minor) adds emotional depth. It shares two notes with the I chord but has a darker quality. Moving between I and vi is one of the most common moves in pop and folk songwriting (C → Am, G → Em, etc.).
Voice Leading and Chord Function
Each diatonic chord has a typical function — where it tends to move next. Understanding these tendencies helps you write progressions with a sense of direction:
- V almost always moves to I (the most powerful resolution in Western music)
- IV can move to I (a plagal cadence, the "amen" ending) or to V
- ii often moves to V, setting up the V–I resolution
- vii° is highly unstable and typically resolves to I
Extending Beyond Triads
Once you're comfortable with diatonic triads, the natural next step is adding 7ths to each chord — which is where the rich, jazzy, or bittersweet sounds come from. See the extended chords article for more.