Key signatures

We’re going to use our interval knowledge to work out notes. We saw earlier how notes in a scale are all connected and belong to what we call a “Key”. The notes that belong in a key are worked out in a certain way. To get these notes, we use a familiar pattern that you have seen already: The Major Scale.

When we work out a Major Key, we have to write the root note for the key we want to start at. Let’s use the key of A as an example.

If we write an A Major scale:

Major Scale

Root     M2      M3      P4      P5      M6      M7

  A         B        C#       D        E        F#       G#

             W        W        H        W       W        W     H  Whole/Half steps

              2         2         1         2        2         2           semi-tones between intervals

              2         4         5         7        9        11          semi-tones from root note

[insert notes in-between but faded out]

With out major scale pattern, we have got a scale that has 3 sharps in there. This tells us that the key of A has 3 sharps and they are always on the notes F, C, and G (there is a reason I wrote them in that order but will talk about that soon!)

So, whenever we play anything in the key of A Major, and we want it to work, those 3 notes have got to have a sharp. So if we play an A Major chord, that will be A C# E. If we want to play an A Major 7 chord it would be A C# E G#.

If we do this for all of our notes and work out all of the keys, we get something that looks a little bit like this:

[insert diagram of all major scales and their accidentals highlighted

Sharps     |     Flats

This is really interesting for 3 reasons. 

1. This now tells us every sharp or flat we need to play when we are in a key. If we know the key of a song, we know which notes we can play now!
2. The order the sharps and fits are in are ordered in a particular way. They are ordered in 5ths.
3. 5th are useful for remembering their order and can be really handy when writing songs.

If we order them with the sharps and flats going up and down, we get something like this

[insert a diagram with the key signatures like this:]

E b b b

B b b

F b

C

G #

D # #

A # # #

Let’s put this in a circle and see what happens:

[insert circle of fifths]

So this isn’t just a circle with random letters around it. This is actually a popular and unique shape in music.

You’ll notice that as we go clockwise, every one of the keys are a fifths apart. This is where the patter on our graph comes in.

The order of the sharps in the Circle of Fifths is this:

F   C   G   D   A   E   B

The most popular way to remember this is:

Father Charles Goes Down And Ends Battle

For the flats, the order is the same, but in reverse:

B   E   A   D   G   C   F

Battle Ends And Down Goes Charles’ Father

Using this saying, we can work out how many Sharps or Flats are in a key. This can be incredibly helpful when we’re playing on a track because we then know which notes to play. This can also be useful when we’re writing songs because we can change to another key. If we change a key in a song it will sound different, but still sound like the same song.