Chord Progressions

A chord progression is a sequence of chords that creates harmonic motion. The choice of progression shapes the emotional feel of music more than almost anything else. Certain progressions have become so common they're essentially part of a shared vocabulary — you've heard the I-IV-V thousands of times without knowing that's what it's called.

The Diatonic Chords in a Key

Build a chord on each note of the major scale using only the notes of that scale. In C major:

I    — Cmaj7   (major, tonic — home base)
ii   — Dm7     (minor, subdominant — movement away)
iii  — Em7     (minor, often like the tonic)
IV   — Fmaj7   (major, subdominant — classic movement before V)
V    — G7      (dominant — creates the tension that resolves to I)
vi   — Am7     (minor, relative minor — often feels like a softer tonic)
vii° — Bm7♭5   (half-diminished, dominant function — rare, tense)

Roman numerals are uppercase for major chords, lowercase for minor. The dominant (V) is typically a seventh chord because the tritone between its 3rd and 7th creates the strongest possible pull toward the tonic.

The ii-V-I

The most important progression in jazz. Three chords that move through subdominant → dominant → tonic:

In C major: Dm7 — G7 — Cmaj7
In F major: Gm7 — C7 — Fmaj7
In B♭:     Cm7 — F7 — B♭maj7

Each chord moves down a fifth (or up a fourth) to the next.
The ii chord prepares the V; the V resolves to the I.

Almost every standard contains ii-V-I progressions. Once you recognise them, you hear them everywhere — and once you know them, you have a framework for improvisation over any standard.

I-IV-V

In C: C — F — G   (or C7 — F7 — G7 in blues)
In G: G — C — D
In A: A — D — E

The backbone of the blues, rock and roll, country, and folk. Three chords are all you need for hundreds of songs. The 12-bar blues is the most codified version of this progression and one of the most important forms in music.

I-V-vi-IV

In C: C — G — Am — F
In G: G — D — Em — C

The "four-chord song" that dominates pop music. Axis of Awesome famously demonstrated that dozens of pop hits use this exact progression. It's effective because the vi chord (relative minor) provides contrast and emotional grounding between the two major chords.

vi-IV-I-V

In C: Am — F — C — G

Start on the relative minor instead and you have a darker variant of the same four chords. "Despacito," "Let Her Go," "With or Without You" — all the same changes, different starting point.

The 12-Bar Blues

I  | I  | I  | I  |
IV | IV | I  | I  |
V  | IV | I  | V  |

In A: A7 | A7 | A7 | A7 |
      D7 | D7 | A7 | A7 |
      E7 | D7 | A7 | E7 |

The last bar (turnaround, usually V) sends you back to the beginning for the next chorus. The basic structure has hundreds of variations — quick changes, altered dominants, tritone subs — but the 12-bar form stays constant.

Diatonic Substitution and Modal Interchange

Borrow chords from the parallel minor to add colour. In C major, borrowing from C minor:

IV (F) → iv (Fm) — from C minor. The minor IV is poignant, often used before I.
                   "Let It Be" uses this: C — G — Am — Fm — C
bVII (B♭) — borrowed major chord, gives a rock/modal feel
bVI (A♭) — borrowed, dramatic. "In My Life" uses ♭VI - ♭VII - I.

These borrowed chords expand the palette beyond the seven diatonic chords without fully modulating to a new key.