Guide to Chord Formation by Howard Wright (Howard@jmdl.com)
Appendix C : Circle of 5ths and Key Signatures

Appendix C : Circle of 5ths and Key Signatures

You've probably heard the phrase 'circle of 5ths' before. It relates to the way key signatures are written, which tells us how many sharps or flats to play.

C major has no sharps or flats G major has one sharp (F#) D major has 2 sharps (F# and C#)

If we carry on finding the keys with 3, 4, 5 sharps we find that the next key in the series is a 5th higher than the previous one.

So when we start with C major, go up a 5th to G major, then up a 5th to D, then A and so on.

It also works for the flat key signatures if we go down in 5ths. So a 5th down from C is F (one flat), then another 5th down is Bb (2 flats), then Eb and so on.

Here is my attempt at drawing it as the famous 'circle' of 5ths (more like an ellipse in my case).

Everytime you move round one position, you go up or down by a 5th. The + signs are for the sharps, the - for the flats. Note that this is for the major keys only.
                         0
             -1                     +1
                         C
                F                 G
      -2                                   +2
         Bb                              D


  -3  Eb                                     A  +3



 -4  Ab                                       E  +4



      Db                                     B
  -5                                            +5


         Gb                              F#
      -6                                   +6
                Cb                C#

             -7                      +7
The only other thing you need to know here is which are the flat and sharp notes.

Here again there is another 5ths relationship.

If we list the sharp notes we need to add as we move clockwise round from C major we get:
F#, C#, G#, D#, A#, E#, B#
So starting from the F#, the series goes up a 5th every time.

So how does it all work?
For G major, from the circle we see it has 1 sharp. Take the 1st sharp from the series above: F#.

So we need F# for a G major scale/key signature.

For D major, we need 2 sharps, so we take F# and C#.

For A major, we take F#, C# and G#.

.. and so on for all the other sharp keys.
For the flat notes, the series is:
Bb, Eb, Ab, Db, Gb, Cb, Fb.
(yet another 5ths relationship...)
So if we pick a flat key, say Eb major, from the circle we see it has 3 flats, so we need Bb, Eb and Ab.
Because all the things you need to know here are connected with relationships of a 5th, it's fairly easy to learn the circle of 5ths. This makes it very easy to work out notes of a scale.

Note that this is all for the major scale.

For minor scales you need to find the relative major key. The relative major key is always 3 semitones higher than the minor key (e.g Cmajor / Aminor - C is 3 semitones above A).
So, say you want to know the scale of Ab minor.

The relative major key is Cb major.

So you need all 7 flats!

The scale is: Ab, Bb, Cb, Db, Eb, Fb, Gb, Ab.
When you see things like Fb, it sounds a bit strange, but it makes things a lot easier if you stick to these conventions instead of saying 'E is the same as Fb'.

The idea is that for every scale, the letter names appear once only. So every scale will have an F of some sort, but in some it will be F natural, some it will be F# and some it will be Fb.


Guide to Chord Formation by Howard Wright
Reformatted and noded (with permission) by Space Butler
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