Key Centers

A key centre (commonly known as key) is the organised collection of notes which provides the harmonic and melodic context in music. The notes contained in a key centre create its’ the fundamental major scale. The notes in a key’s major scale is the basis for the construction of chords and scales

Key Signature

Similar to how a time signature determines a rhythmic time grid in music, a key signature is an identifier that tells the reader the overall key centre. Both signatures are commonly found at the beginning of a piece of music.

Circle of 5ths

The Circle of 5ths is a diagram used to illustrate the organisation of key signatures. The Circle of 5ths labels all 12 key signatures mapped in intervals of 5ths along a circle’s radius. Keys are organised into two groups: sharps and flats; starting from the centre key C Major, all sharp keys are ordered in a clockwise direction and all flat keys are ordered in a anti-clockwise direction. The ordering of keys is determined by the number of sharps/flats contained within a key. Above the circle are the ordered arrays of sharps and flats used to determine which notes are found within a particular key.

Flats ♭

B♭, E♭, A♭, D♭, G♭, F♭, C♭

Sharps ♯

F♯, C♯, G♯, D♯, A♯, E♯, B♯

Circle of 5ths

C

G

D

A

E

B

Gb/ F#

Db

Ab

Eb

Bb

F

C♭

C#

G#

D#

A#

0

1

2

3

4

5

6

5

4

3

2

1

7

7

8

9

10

Identifying Key Signatures

By using the Circle of 5ths we can identify the properties of each key’s signature, which are the number and name of a key centre’s sharps/flats. We can identify these properties via determining position on the circle then utilising the ordered array of either sharps or flats.

Example

To determine the key signature properties of A major:

1. We can identify via its’ position in the circle that the key A major contains 3 sharps.
2. We can then ascertian by looking at the sharps array that these 3 sharps must be F♯, C♯, and G♯.

Constructing a Key Centre’s Major Scale

Once we have determined the properties of a key signature, we can then proceed to construct a major scale pertaining to that key centre. This is performed by combining the notes from within a key signature with the remainding natural notes in music.

Example

After we have established the key signature properties of A major (Steps 1 & 2), we can then determine the A major scale pertaining to that key:

3. To determine a key centre’s major scale we combine and order both the note groups from within the key signature of A major (F♯, C♯, G♯) with the remainder natural notes in music (A, B, D, E), to construct an A major scale: A, B, C♯, D, E, F♯, G♯.

Theoretical vs. Practical Application

Labelling notes such as B♯, E♯, C♭, F♭, although theoretially correct in certain keys, becomes impractical in playing situations and should be avoided.

Key Properties Index

Key Centre	No. Sharps/Flats	Key Signature	Major Scale
C Major	0	nil	C, D, E, F, G, A, B

Key Centre	No. Sharps	Key Signature	Major Scale
G Major	1	F♯	G, A, B, C, D, E, F♯
D Major	2	F♯, C♯	D, E, F♯, G, A, B, C♯
A Major	3	F♯, C♯, G♯	A, B, C♯, D, E, F♯, G♯
E Major	4	F♯, C♯, G♯, D♯	E, F♯, G♯, A, B, C♯, D♯
B Major	5	F♯, C♯, G♯, D♯, A♯	B, C♯, D♯, E, F♯, G♯, A♯
F♯ Major	6	F♯, C♯, G♯, D♯, A♯, E♯	F♯, G♯, A♯, B, C♯, D♯, E♯
C♯ Major	7	F♯, C♯, G♯, D♯, A♯, E♯, B♯	C♯, D♯, E♯, F♯, G♯, A♯, B♯
G♯ Major	8	F♯, C♯, G♯, D♯, A♯, E♯, B♯	C♯, D♯, E♯, F♯, G♯, A♯, B♯, F♯♯
D♯ Major	9	F♯, C♯, G♯, D♯, A♯, E♯, B♯	C♯, D♯, E♯, F♯, G♯, A♯, B♯, F♯♯, C♯♯
A♯ Major	10	F♯, C♯, G♯, D♯, A♯, E♯, B♯	C♯, D♯, E♯, F♯, G♯, A♯, B♯, F♯♯, C♯♯, G♯♯

Key Centre	No. Flats	Key Signature	Major Scale
F Major	1	B♭	F, G, A, B♭, C, D, E
B♭ Major	2	B♭, E♭	B♭, C, D, E♭, F, G, A
E♭ Major	3	B♭, E♭, A♭	E♭, F, G, A♭, B♭, C, D
A♭ Major	4	B♭, E♭, A♭, D♭	A♭, B♭, C, D♭, E♭, F, G
D♭ Major	5	B♭, E♭, A♭, D♭, G♭	D♭, E♭, F, G♭, A♭, B♭, C
G♭ Major	6	B♭, E♭, A♭, D♭, G♭, F♭	G♭, A♭, B♭, C, D♭, E♭, F♭
C♭ Major	7	B♭, E♭, A♭, D♭, G♭, F♭, C♭	C♭, D♭, E♭, F♭, G♭, A♭, B♭