Circle of fourths (or fifths)

For many people consulting this site, this will have become apparent even before they read this page, but whilst they may have recognised the phenomenom (and have almost certainly heard people ranting on about circle of fourths) they may still not realise the connection.

Circle of fourths

works like this:

Every key has three chords which are 'fundamental' to it. They are three major chords at fixed and predicatable intervals - as, for instance in C the chords C, F and G.

Note straight away that the interval between C and F is what is called a fourth (because....see earlier articles, and in particular chordbuilding 3), and also that the interval from C to G is a fifth.

The explanation

(I am for the moment going to do everything in C, simply because using material from Chordbuilding 3 and the 12 bar blues book you will be able to work out how to transpose the whole into other keys).

When you play a G chord and then add a seventh to it, the ear tells you that it is heading to another chord, and that chord you will either already know or will come to realise is C - a fourth above the G.

If we now play that C chord and add the seventh to it, the same sensation will occur, and it will become apparent that the chord it is leading to is F - a fourth above C.

With F then F7 the next chord will be Bb.....Bb7....Eb.....Eb7.....Ab.....etc.

If we continue in this way for long enough we will go right through every basic and 7th major chord there is and come back to C.

The only justification for referring to this as a circle of fifths that I can find is that when you count in the other direction (ie C back to G, G back to D, etc.) then the interval is a fifth. So C is a forth above G, but counting the other way round, G is a fifth below C.

This phenomenom is quite naturally used by people writing music often without ever having analysed what is going on. It is one of the fundamentals, and if you look at the chord sequence for some pop song you will in 9 out of 10 cases find that the circle of fourths is what most of it is about. I will give you one sequence here that shows the kind of thing you might find in a pop song of almost any period from 1890 to the present day:-

         II   C    I    E7   I    A    I    A7   I

         I    D7   I    G7   I  C. F.  I    C    II

What happens here is that the writer, trying to break away from circle of fourths optimistically jumps from C to E as a first move......but then the next few chords are all jumping from one fourth to the next until he/she comes back to C by a final fourth!

So what? A million people have done it before, but it still sounds good.

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