What is the circle of fifths?

The Circle of Fifths is a harmonic system which uses the interval of a 5th, i.e. C to G to help us identify keys and other important musical factors. The Circle of Fifths can be laid out in many ways but this one is my favourite. (See whiteboard). This allows us to lay out the Circle of Fifths in a way that the eye can logically follow, with all the information present.