The chords of a key · From Zero to Mozart

Build a triad on every degree of a scale, using only that key's notes, and you get seven chords — the harmonic vocabulary of the key. And the pattern of which chords are major, minor or diminished is the same in every major key, so you learn it once.

The seven triads of a major key

Degree	1	2	3	4	5	6	7
Roman numeral	I	ii	iii	IV	V	vi	vii°
Quality	major	minor	minor	major	major	minor	diminished
in G major	G	Am	Bm	C	D	Em	F♯°

UPPER-CASE numeral = major triad. Lower-case = minor. A little ° = diminished. You can read a whole harmonic analysis — I, IV, V, vi — without naming a single letter.

76 bpm

The three major triads of G major, as broken chords: I (G–B–D), IV (C–E–G), V (D–F♯–A). These three do most of the work in any key.

In a minor key, using the harmonic-minor raised 7th (which gives a strong V), the pattern is i – ii° – III⁺ – iv – V – VI – vii°. In E minor: Em – F♯° – G⁺ – Am – B – C – D♯°. The three you'll actually use are i, iv and V.

What the chords are for — three jobs

Every chord belongs to a function family:

Function	Chords	Feel
Tonic (T)	I, vi	home, rest
Predominant (PD)	IV, ii	stepping away from home, building
Dominant (D)	V, vii°	maximum tension — must resolve to I

The standard shape of a phrase is T → PD → D → T: home, step away, tension, home. Once you hear that arc, you hear the skeleton of almost every tune you've played.

50 bpm

I – IV – V – I in G major (G–B–D, C–E–G, D–F♯–A, G–B–D), written as block chords so you can see the harmony (a violinist rolls or breaks them). Home, away, tension, home. Play the roots — G, C, D, G — and feel the D pull back to the G.

Try it

The chords of a key

The usual mistake

Learning the chords of each key as a separate list. They follow one pattern — major, minor, minor, major, major, minor, diminished — in every major key. Learn the pattern and the roman numerals, and you can name the chords of any key on sight and know what each one is likely to do next.