Key signatures are used so that we don't have to write sharp or flat signs next to every note.
Key signatures are written using either sharps, or flats.
The keys that use sharps in their key signatures are:
G, D, A, E, B, F#, C#The keys that use flats in their key signatures are:
F, Bb, Eb, Ab, Db, Gb, CbYou will notice that the key of C is not mentioned above. That is because the key of C contains no sharp or flat notes. On a keyboard, the C major scale is only the white notes, from C to C, and contains no black notes. Therefore, if there is no key signature in a piece of music, it is in the key of C major (or it's relative minor, A minor).
The table below shows the key, and the number of sharps in that key.
Sharp key signatures
C -- 0
G -- 1
D -- 2
A -- 3
E -- 4
B -- 5
C#-7To remember the order of the sharp key signatures this sentence can be used:
Good Dogs Always Eat Big Fat Cats
The table below shows the key, and the number of flats in that key.
Flat key signatures
C -- 0
F -- 1
Bb -- 2
Eb -- 3
Ab -- 4
Db -- 5
Gb -- 6
Cb -- 7To remember the order of the flat key signatures this sentence can be used:
Flats Become Easier After Drinking Guinness Cold
Now that you know how many sharps/flats are in each key, you need to know which notes are sharp/flat in each key.
A great technique for remembering this is using the sentences:
Father Charles Goes Down And Ends Battle (Order of the sharps in a key signature)
Battle Ends And Down Goes Charles' Father (Order of the flats in a key signature)
The sharps and flats in a key signature appear in this order in key signatures, and are also written on the stave in this order.
So, for example, lets look at the key of A major. We know that A major contains 3 sharps, because "Good (1), Dogs (2), Always (3)..."
Now, we need to know what notes these 3 sharps are. So.. Father (1), Charles (2), Goes (3) ...
So we know that the three sharps in A major are F# C# and G#
Lets look at another example, this time a flat key, Db major.
We know that Db major contains 5 flats because 'Flats (1), Become (2), Easier (3), After (4), Drinking (5)...'
We also know that these flats are Bb, Eb, Ab, Db, Gb... Because 'Battle (1), Ends (2), And (3), Down (4), Goes (5)...'
This method for memorizing key signatures is among the greatest methods, as with time, you naturally learn the amount of sharps and flats in the different keys, and the order of the sharps and flats, without saying the sentences.
Relative Minor KeysThe relative minor scale/key of every major scale/key is found by looking at the sixth note of the major scale. The table below shows this:
Sharp key signatures:
C Major -- A Minor
G Major -- E Minor
D Major -- B Minor
A Major -- F# Minor
E Major -- C# Minor
B Major -- G# Minor
F# Major -- D# Minor
C# Major -- A# Minor
Flat key signatures:
C Major -- A Minor
F Major -- D Minor
Bb Major -- G Minor
Eb Major -- C Minor
Ab Major -- F Minor
Db Major -- Bb Minor
Gb Major -- Eb Minor
Cb Major -- Ab MinorTo determine if a piece is in the major or relative minor key, you have to look at the piece in more detail. As a very basic rule, you can look at the first and last notes/chords of a piece. For example, if the key signature of a piece has 2 flats, it could be Bb major or G minor. If the last chord in this piece is a Bb major, you know the key is Bb major. If the last chord of the piece is G minor, you know the piece is in G minor.
This is a lot of information to take on board all at once, and it can take a bit of time for this to really cement itself in your head, but the more you revise it and use it, the easier it becomes to understand and the better you get at it!
Getting this basic piece of theory down will allow you to move on to more complex things too, such as using scales, harmony, modes and more!
Hopefully you find this lesson helpful! If anyone has any questions, please post a comment and I will try to answer it with a reply!