The harmonised major scale

The pattern

Take any major scale. Build a triad on each scale degree using only notes from that scale. The result is the harmonised major scale — the source of nearly every chord progression you’ve ever heard.

In C major (C D E F G A B), build a triad on each note:

Degree	Triad notes	Chord	Quality	Roman
1	C E G	C	major	I
2	D F A	Dm	minor	ii
3	E G B	Em	minor	iii
4	F A C	F	major	IV
5	G B D	G	major	V
6	A C E	Am	minor	vi
7	B D F	B°	diminished	vii°

This pattern of qualities — Major - minor - minor - Major - Major - minor - diminished — is the same in every major key.

Memorise this pattern. It’s the most important fact in functional harmony.

Why the qualities turn out this way

You only used notes from the major scale. When you stack two thirds on the 1, you happen to land on intervals of M3 + m3 — that’s a major triad. Stack on the 2 and you get m3 + M3 — that’s minor. And so on. The pattern emerges from the scale’s whole-/half-step structure.

The harmonised minor scale

Apply the same idea to a natural minor scale and you get a different pattern:

Degree	Quality	Roman
1	minor	i
2	diminished	ii°
3	major	♭III
4	minor	iv
5	minor	v
6	major	♭VI
7	major	♭VII

Most minor-key pop and rock uses harmonic minor to get a major V chord — because the V→i resolution is so much stronger when V is major than when v is minor. We’ll see this in Chord Progressions.

Why this matters

Any chord progression you analyse in a piece will (almost always) use chords from one of these two diatonic sets. “Don’t Stop Believin’” is I-V-vi-IV in E major. “Stand By Me” is I-vi-IV-V in A major. “Hit the Road Jack” is i-♭VII-♭VI-V in A minor.

Once you know the diatonic chord set, you can:

• Analyse any song to figure out what key it’s in.
• Transpose any progression to a new key instantly.
• Compose new progressions that sound finished and right.

7th-chord version (jazz default)

Harmonise the scale in 7ths instead of triads:

Degree	Chord	Roman
1	Cmaj7	Imaj7
2	Dm7	iim7
3	Em7	iiim7
4	Fmaj7	IVmaj7
5	G7	V7
6	Am7	vim7
7	Bm7♭5	viim7♭5

The crucial one: V7 — the only dominant 7 chord in the major-scale harmonisation. This is what makes the V→I cadence pull so hard.

Try this

Play through the harmonised C major scale: C, Dm, Em, F, G, Am, B°, C. Listen to how each chord feels. The majors (I, IV, V) are bright. The minors (ii, iii, vi) are introspective. The B° feels uneasy.

Now play it in 7ths: Cmaj7, Dm7, Em7, Fmaj7, G7, Am7, Bm7♭5, Cmaj7. Same functions, more sophisticated colour.

Then transpose the whole exercise to G major: G, Am, Bm, C, D, Em, F♯°. Same pattern. Different key.

Once you can do this in five keys without thinking, the harmonic foundation of all of pop and most of jazz is yours.