# Keys and key signatures

*Module 5 · Lesson 4: The major scale and keys · BazzLow*

> Understand what a key is and why each major key has its own set of sharps or flats.

Before this lesson: [5.1 The major scale formula](https://bazzlow.com/en/major-scale-and-keys/major-scale-formula/) · [3.5 Accidentals and key signatures on the staff](https://bazzlow.com/en/reading-music/accidentals-and-key-signatures/)

Lesson 3.5 showed what a key signature does on the staff. Now we can say where it comes from: it comes from the scale of the key.

## What a key is

A piece is “**in the key of** G major” when it uses mainly the notes of the G major scale and feels resolved on G. A **key** is a tonic plus its scale. Other notes can still appear, written as accidentals.

## Why each key has its own signature

Each major key has a fixed set of sharps or flats: the ones its scale needs. That set is its **key signature**. A key signature has either sharps or flats, never both.

> **Diagram:** Key signatures on the bass clef staff: G major has one sharp; D major has two sharps; F major has one flat; B♭ major has two flats.

## The 15 major keys

*The 15 major key signatures, each with its scale.*

| Major key | Key signature | Scale |
| --- | --- | --- |
| C | 0 | C D E F G A B |
| G | 1 ♯ | G A B C D E F♯ |
| D | 2 ♯ | D E F♯ G A B C♯ |
| A | 3 ♯ | A B C♯ D E F♯ G♯ |
| E | 4 ♯ | E F♯ G♯ A B C♯ D♯ |
| B | 5 ♯ | B C♯ D♯ E F♯ G♯ A♯ |
| F♯ | 6 ♯ | F♯ G♯ A♯ B C♯ D♯ E♯ |
| C♯ | 7 ♯ | C♯ D♯ E♯ F♯ G♯ A♯ B♯ |
| F | 1 ♭ | F G A B♭ C D E |
| B♭ | 2 ♭ | B♭ C D E♭ F G A |
| E♭ | 3 ♭ | E♭ F G A♭ B♭ C D |
| A♭ | 4 ♭ | A♭ B♭ C D♭ E♭ F G |
| D♭ | 5 ♭ | D♭ E♭ F G♭ A♭ B♭ C |
| G♭ | 6 ♭ | G♭ A♭ B♭ C♭ D♭ E♭ F |
| C♭ | 7 ♭ | C♭ D♭ E♭ F♭ G♭ A♭ B♭ |

Three pairs are **enharmonic keys**: the same sounds written two ways. B = C♭, F♯ = G♭ and C♯ = D♭. So there are 12 different-sounding major keys, but 15 written ones. A key that would need more than 7 accidentals, such as D♯ major with 9 sharps, is a **theoretical key**: it is written enharmonically instead (E♭ major).

## Why different keys exist

- singers’ ranges;
- easier fingering on some instruments: guitar and bass favour E, A, D and G, horns favour flat keys such as B♭ and E♭;
- the sound of open strings.

## Try it

Using the shape from lesson 5.3, play the scales of G, D and A major. For each, say the sharps as you play them.

## New terms

- key
- key signature
- enharmonic key
- theoretical key

Page: https://bazzlow.com/en/major-scale-and-keys/keys-and-key-signatures/