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• We previously learnt about common key signatures and how the key signature specifies the key, the scale and the key note.

• This table shows all possible key signatures and the major and minor keys they specify:
• It also shows which sharps and flats are in each key signature:
• So, for example, the key of Ab major (the fourth row down) has four flats in its key signature, and they are Bb, Eb, Db and Ab;
• The key of C# minor (fourth row up from the bottom) has four sharps in its key signature, and they are F#, C#, G# and D#.
• This makes very clear the patterns that exist in the sharps and flats of the key signatures - see the "circle of fifths" below.

Major scale/
key note
Minor scale/
key note
Sharps -->     <--Flats
FCGDAEB
CbAbbbbbbbb
GbEb bbbbbb
DbBb  bbbbb
AbF   bbbb
EbC    bbb
BbG     bb
FD      b
CA
GE#
DB##
AF####
EC#####
BG######
F#D#######
C#A########

• As is clear from this table, the sharps or flats in a key signature are always written in the same order, working from the left in the examples below, and they are always written in these positions on each stave:

• The key signature is written at the start of every line of music, not just the first one.

• The order of notes in the list of sharps and flats is the same (circularly) as the list of key signatures themselves: C, G, D, A, E, B, F.
• They are all the same as in the circle below.
• The next note going clockwise is calculated by going up five notes (counting inclusively)
• This is the same as increasing the frequency by 1.5 (3/2).

• Here is one explanation of why key signatures are needed, and what their purpose is: