# Chords in a key

A key is a scale; stacking thirds on each scale note gives seven chords that belong together. Number them and every key reads the same — for a bass player, the number says which root comes next and how far to move.

## Seven chords from one scale

I major · ii minor · iii minor · IV major · V major · vi minor · vii° diminished. In E: E F♯m G♯m A B C♯m D♯°. You play the root of each.

## The keys you will meet first

| Key | I | ii | iii | IV | V | vi | vii° |
|---|---|---|---|---|---|---|---|
| E | E | F♯m | G♯m | A | B | C♯m | D♯° |
| A | A | Bm | C♯m | D | E | F♯m | G♯° |
| D | D | Em | F♯m | G | A | Bm | C♯° |
| G | G | Am | Bm | C | D | Em | F♯° |
| C | C | Dm | Em | F | G | Am | B° |

## One string, three numbers

On one string the IV is five frets above the I and the V is seven. Open E, 5, 7 = E A B. Open A, 5, 7 = A D E. Start at E-string fret 5 and the same three frets (5, 10, 12) give the key of A.

## Progressions by number, as roots (in E)

- I–IV–V–I: E A B E
- I–V–vi–IV: E B C♯m A
- vi–IV–I–V: C♯m A E B
- I–vi–IV–V: E C♯m A B
- ii–V–I: F♯m B E — see [Walking bass](walking.md)

## Root and fifth

From any root, the fifth is one string up and two frets up. I–IV–V–I as root–fifth: E B · A E · B F♯ · E B.

## Why V wants to go home

The third of V (D♯ in B) is the key's seventh note, a half step under the root. B → D♯ → E.

## Minor keys

The relative minor is the vi: C♯m for E. Minor songs often borrow a major V from harmonic minor.

## Find the key of a song

List the chords, find the row holding them all, check the last chord. E A B C♯m → E; G C D Em → G; Am F C G ending on Am → A minor.

## Ready when

- Play I, IV and V of E, A, D and G on one string without the table.
- Name a song's key from its chords and play the roots in another key.
- Play root and fifth under any chord of an I–V–vi–IV loop, and hear the V about to land.