The Circle of fifths is a visual method of showing the relationship between keys.
If you begin at the top of the circle on C major/A minor and proceed one step clockwise (to the right), the next key is G major/E minor, and is five notes higher than C major. Proceeding one step more to the right we reach D major/B minor which is again five steps higher than G major. If we continue to proceed clockwise all of the keys will be a fifth higher than the previous key and we would eventually return back to C major. Notice that B major, F sharp major and C sharp major can be written enharmonically as C flat major, G flat major and D flat major respectively. The ability of these keys to be written enharmonically allows the circle of fifths to ‘pass’ from keys which have sharps in their key signatures to those which have flats.
If we start again at C major/A minor and proceed one step anticlockwise (to the left), the next key is F major/D minor which is five notes lower than C major. If we continue anticlockwise all of the keys are five notes lower than the previous key.
Notice that, whichever way we proceed the key signature increases: by one sharp – if we are moving clockwise – or one flat – if we are moving anticlockwise. The circle of fifths is a great way of learning key signatures, enharmonic equivalents and the relationship between keys.
In many styles of music fifth relationships, based on the circle of fifths, are used in passages which modulate to a different key, or move through various chords, or notes, within the same key.
For example, a melodic pattern may be moved through various diatonic notes which have a fifth relationship.
In this example, each quarter note beat begins and ends on a note which is a fifth higher than the following note. If we related this to the circle of fifths we would be moving anticlockwise from C major. However, because this example remains in a single key, C major, the flat keys which follow after F major in the circle of fifths are not used. Instead, our example moves through B – E – A – D – G and back to C. If we wanted to continue to relate this to the circle of fifths, we would have to say that the fifth cycle has moved across to the key of B major and moves back to C from there. It is important to remember that the fifth relationship between these notes is only based on the circle of fifths and, as we have already seen, does not follow the circle explicitly.
As well as basing melodic elements on fifth cycles, composers also relate chords to each other by this method. In the following example, the progression uses a fifth cycle to move from the mediant to the tonic of C major, and, as with the previous example, the root movement of the chords is based on the circle of fifths.
Fifth relationships can also be used as a means of modulation.