KEY  SIGNATURES
The Key Signature simplifies music notation and tells musicians the key of a song and which notes have accidentals (Sharps or Flats).   Key Signatures are used to reduce adding Sharps or Flats beside Notes in written Music every time one is required.   For example, if we start a song on the C note, sharps and flats aren't required, but if we start the same song on C# or Cb, then 7 sharps or 7 Flats would be required to be added beside each written note.

Since Music only has 7 Letter Names (A - G) there are 15 Key Signatures,
7 Flat Keys - 7 Sharp Keys & 1 Key with No sharps or flats.   The following table is the list of 15  Major Key Signatures:

No. of 's or 's
Sharp Keys
Flat Keys
0
C
1
G      
F      
2
D     
B
3
A     
E
4
E     
A
5
B     
D
6
F
G
7
C
C
There is an established order in which SHARPS must appear in key signatures:
F  C  G  D  A  E  B

To remember the Order of SHARPS there is an old simple rhyme:
Father  Charles  Goes  Down  And  Ends  Battle

FLATS must appear in the reverse order:
B  E  A  D  G  C  F

Reverse the same rhyme for the Order of FLATS:
Battle  Ends  And  Down  Goes  Charlie's  Father
Here is how they are placed on the Staff for the Treble and Bass Clefs:
 

In the Alto and Tenor Clefs they are placed as follows:
 
MINOR   KEY  SIGNATURES

For every MAJOR Key Signature there is a Relative MINOR Key Signature.   The most common way to describe the difference in sound between the two is that Major Keys sound Happy while Minor keys sound Sad.

They are called Relative because the Key Signatures look the same but the scales for each one sounds different.   The RELATIVE MINOR of any Major Key is found on the 3rd note of the Major Key.   For example the notes of the C Major Scale are:
C   D   E   F   G   A   B   C

The 6th note of the C Major Scale or Key is A, so A Minor is Relative to C Major.   This means that C Major has the Same Key Signature as A Minor but the starting notes are different, so the notes of the A Minor Scale are:
A   B   C   D   E   F   G   A
Table of Relative MAJOR and MINOR Key Signatures

MAJOR
Sharp Keys
MINOR
       
MAJOR
Flat Keys
MINOR
 
 
  A    C 
   
G
E
 
F
D
D
B
 
Bb
G
A
F#
 
Eb
C
E
C#
 
Ab
F
B
G#
 
Db
Bb
F#
D#
 
Gb
Eb
C#
A#
 
Cb
Ab

Comparing the C Major Scale/Key The A Minor Scale/Key



Notice that the Key Signatures for C Major and A Minor (Relative Minor) is the exact same.   The Scales Notes are also the exact same EXCEPT that starting note for each scale is different.   This difference is what provides each Key and Scale with a Different Sound and Feel.
C Major Scale
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A Minor Scale
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