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  • Writer's pictureTom Glasson

Introduction to Key Signatures

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How the circle of 5ths works. The order of sharps and flats.
Circle of 5ths

Key Signature basics

The key signature is the key to the combination of notes which will be used in the music. In musical score they are shown by sharp of flat symbols before the time signature like these.

Each key uses all 7 lettered notes and the key signature tells us if any of the notes are sharp or flat.

For example:

C Major - C, D, E, F, G, A ,B

D Major - D, E, F#, G, A, B, C#

A Major - A, B, C#, D, E, F#, G#

Bb Major, Bb, C, D, Eb, F, G, A

You can see that every letter is always included. But different keys have different sharps or flats - The key is either sharp OR flat, they never include both.

The sharps or flats which appear in key are based on the Major scale. Read more about the scales here.

Simply, if you start on any note and play this formula:

Tone, Tone, Semitone, Tone, Tone, Tone, Semitone

You will have played the major scale - these are the notes which will be in the key.

(A semitone is the distance between one note and the very next note, 1 key on a keyboard. A tone is two semitones, or 2 keys).

Watch the video above for an example, or read the article on major scales to learn more.

C Major is the natural major key, that's why it is at the top of the circle and has no sharp or flats.

The Circle of 5ths

Starting with C Major at the top, going around clockwise to the right, are the sharp # Keys, and around to the left are the flat b keys.


The keys are built in 5ths, so going around right, each key is a 5th above the last, so after C is G, because G is a 5th Above C.

Then the next key is D, which is a 5th Above G and so on in this order:

C Major - Natural

G Major - 1 Sharp

D Major - 2 Sharps

A Major - 3 Sharps

E Major - 4 Sharps

B Major - 5 Sharps

F# Major - 6 Sharps

The sharps in the keys build upon each other, so the first sharp is F# (In G major) then the next key, D Major has 2 sharps, starting with the F# and adding C#. So the sharps appear in this order:

C Major (0) - Natural

G Major (1) - F#

D Major (2) - F#, C#

A Major (3) - F#, C#, G#

E Major (4) - F#, C#, G#, D#

B Major (5) - F#, C#, G#, D#, A#

F# Major (6) - F#, C#, G#, D#, A#, E#

The sharps are added in 5ths, and if you look at the circle, they are kind of added in the same order as the key signatures, starting with F and moving around. F, C, G, F, A & E.

The new sharp added in each key is one semitone lower than the new key, so E Major adds a D#, which is a semitone lower than E, B major adds A# etc...


The flats work in a similar way, but going around to the left (anticlockwise), they actually build in 4ths.

C to F is a 4th

Then the next key is Bb, which is a 4th above F and so on in this order:

C Major - Natural

F Major - 1 Flat

Bb Major - 2 Flats

Eb Major - 3 Flats

Ab Major - 4 Flats

Db Major - 5 Flats

Gb Major - 6 Flats

The flats build on each other the same way as the sharps. So they appear in this order:

C Major (0) - Natural

F Major (1) - Bb

Bb Major (2) - Bb, Eb

Eb Major (3) - Bb, Eb, Ab

Ab Major (4) - Bb, Eb, Ab, Db

Db Major (5) - Bb, Eb, Ab, Db, Gb

Gb Major (6) - Bb, Eb, Ab, Db, Gb, Cb

The new flat added is the name of the next key signature.

Have a good look at the image and study how the patterns work, it is fairly simple and once you get your head around it, you will have a good understanding of music and how the keys relate to each other.

A Free Gift for you...

Download the Grade 1 Music Theory Workbook - An Introduction to Music Theory for free. The workbook is a written course which teaches you the entire content of Grade 1 music theory from start to finish, it is the full written version of our video course. It contains activities, with answers, to test your knowledge and give you chance to practice what you are learning.

There are 19 sections, covering every topic as well as reference sheets and materials which will come in handy as you study.

Click here to check it out.

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