Lesson 20 · Part 5, A key is chords and scale together

Progressions

The chords on the first, fourth and fifth degrees carry a great many songs, and the fifth pulls the music back home.

Shapes for each chord

C I
13113153fr1513513
Dm ii
51♭310fr151♭3515fr151♭355♭3
Em iii
515151♭31
F IV
1513511513513511513
G V
13113511311
Am vi
51♭351♭35fr151♭3511♭3
B° vii°
1♭52fr1♭51♭31♭3♭51♭5♭3♭5

These are the most playable shapes for each chord, starting from the lowest position. Every shape fits within the reach of one hand, so none of them needs a finger you do not have.

Progressions in C major

Three chord
  1. IC
  2. IVF
  3. VG
CIFIVGVCCBEFDGAG−1+1−3+2−2

One of the six lines between these chords is flat: that note belongs to both chords, so it stays where it is. No voice moves more than three semitones.

Every one of these chords comes from C major.

Axis
  1. IC
  2. VG
  3. viAm
  4. IVF
CIGVAmviFIVCBCCEDEFGGAA−1+1−2+2+1+2

Three of the nine lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than two semitones.

Every one of these chords comes from C major.

Doo-wop
  1. IC
  2. viAm
  3. IVF
  4. VG
CIAmviFIVGVCCCBEEFDGAAG−1+1−3+2−2

Four of the nine lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than three semitones.

Every one of these chords comes from C major.

ii–V–I
  1. ii7Dm7
  2. V7G7
  3. Imaj7Cmaj7
Dm7ii7G7V7Cmaj7Imaj7CBBDDCFFEAGG−1−2−1−2

Four of the eight lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than two semitones.

These are the third and the seventh of each chord on their own. Together they decide whether a chord is major, minor or dominant, which is why they are called guide tones. If you play only these two notes, you can still hear the chords change. If you play only the root and the fifth, you cannot. Two of the four lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than one semitone.

Dm7ii7G7V7Cmaj7Imaj7CBBFFE−1−1

Every one of these chords comes from C major.

Rhythm changes
  1. Imaj7Cmaj7
  2. vi7Am7
  3. ii7Dm7
  4. V7G7
Cmaj7Imaj7Am7vi7Dm7ii7G7V7CCCBEEDDGGFFBAAG−1−2−2−2−2

Seven of the twelve lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than two semitones.

This diagram again follows only the guide tones, the third and seventh of each chord. Two of the six lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than three semitones.

Cmaj7Imaj7Am7vi7Dm7ii7G7V7EGFFBCCB+3−2+1−1

Every one of these chords comes from C major.

Twelve-bar blues
  1. I7C7
  2. I7C7
  3. I7C7
  4. I7C7
  5. IV7F7
  6. IV7F7
  7. I7C7
  8. I7C7
  9. V7G7
  10. IV7F7
  11. I7C7
  12. V7G7
C7I7F7IV7C7I7G7V7F7IV7C7I7G7V7CCCDCCDEE♭EFE♭EFGFGGFGGB♭AB♭BAB♭B+2−2+2−1+1+1−2+1+1−2+2−2+2−1+1+1−2+1+1

Five of the 24 lines between these chords are flat: those notes belong to both chords, so they stay where they are. No voice moves more than two semitones. The progression lasts twelve bars, but a repeated chord is not a change, so the ladder shows only the six places where the harmony moves.

This diagram again follows only the guide tones, the third and seventh of each chord. None of the twelve lines between these chords is flat, so every voice moves at every change. No voice moves more than two semitones. The progression lasts twelve bars, but a repeated chord is not a change, so the ladder shows only the six places where the harmony moves.

C7I7F7IV7C7I7G7V7F7IV7C7I7G7V7EE♭EFE♭EFB♭AB♭BAB♭B−1+1+1−2+1+1−1+1+1−2+1+1

Two of these chords go outside C major, borrowing B♭ and E♭ (C7, F7). No single key contains all of them. Every one is a dominant seventh, and a dominant seventh pulls towards the chord whose root is a fifth below its own, one step anticlockwise on the circle (C7 → F, F7 → B♭, G7 → C). A chord drawn dashed, here and on the circle, goes outside the key.

There are six progressions in C major, including Three chord (C F G) and Axis (C G Am F).

Each row is one progression. It is written first in roman numerals, which name each chord by the degree of the scale it is built on, and then as the chords those numerals stand for in this key. A dashed outline means the chord borrows a note that C major does not contain. Under each progression, a diagram follows every note from one chord to the next. A flat line is a note that stays where it is, and a sloped line is labelled with the number of semitones the note moves.

A great many familiar songs use just three chords: the one built on the first degree of the scale, the one on the fourth and the one on the fifth. They are written with Roman numerals as I, IV and V. In C those chords are C, F and G.

The chord on the fifth degree has a particular role. It contains the seventh degree of the scale, B in the key of C, which sits a semitone below the tonic, the home note, and pulls strongly towards it. If you play C, F and G and then stop, the G does not sound finished. When you play C after it, you hear the music arrive home.

Much of harmony works by setting up that expectation and then meeting it, delaying it or avoiding it.