Lesson 21 · Part 5, A key is chords and scale together

What moves between the chords

Most notes barely move when chords change, which is why a progression sounds connected.

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.

When you play a C chord, you play three notes at once. When you change to F, you play three notes again, not all of them the same. Your ear does not hear this as one block replacing another. It hears individual notes moving, and most of them move only a short way.

Imagine three singers instead of six strings. One sings the bottom note, one the middle and one the top, and each has to go somewhere when the chord changes. A good arranger does not make all three jump. They choose the version of F that is nearest to the C everyone is already singing, so one singer holds the same note and the other two step by a semitone or two. Each of those singing parts is called a voice. The diagram below follows every voice across the changes, and a flat line shows a note that does not move at all.

A guitar hides this completely. You learn chords as shapes, so you form one shape, lift your whole hand and form another, and your hand jumps even when the notes barely move. A piano player feels the notes that stay, because their fingers stay on those keys. Nothing about a fretboard tells you which of the six strings is still carrying the note it carried a moment ago.

This also explains why inversions are useful. An inversion is a chord with a note other than the root in the bass. It is not a harder way to play a chord you already know. It is often the version of that chord nearest to the notes you are already playing, and that is what makes the change sound smooth rather than abrupt.

Where the chords have sevenths, the page shows a shortcut beneath the diagram: the third and the seventh on their own. Those two notes decide whether a chord is major, minor or dominant. The root says much less about the chord’s character, and in a band the bass player is usually playing it anyway. If you play only the thirds and sevenths through a set of changes, you can still hear what each chord is. If you play only the roots and fifths, that information is lost.