First, everything starts from C, since C is the key in which there are NO sharps or flats.
As we move clockwise from C, each note is a fifth above the last. So G is the fifth of the C scale, D is the fifth of the G scale, and so on.
Starting with G, each new key going clockwise has one more sharp note in its major scale.
If we move counterclockwise from C, each note is a fifth below the prior note. And, just as with sharps, each scale to the left of C adds a flat note.
What Does the Circle of Fifths Do for a Musician?
First and foremost, it gives us a quick visual reference to a lot of information about all 12 keys in music.
Again, C is the reference point, but these concepts will apply for any key.
We already know that G is the fifth of the C scale. In the Circle of Fifths, the fifth note of the scale always sits just to the right of the root note.
And we already know that F is a fifth below C. But we should also note that the fifth note below any root note is the same named note as the fourth note of the key scale.
OK, sounds confusing, so let's break it down. Here's the C scale in two octaves: C D E F G A B C D E F G A B C
Using the middle C as number 1, count down (left) to the fifth note. Is it F? Should be. Now count up (right) to the F note. Is it the fourth note? If not, you miscounted. So now we know the following is true:
5th below Root = 4th above Root
What is a relative minor?
The relative major and minor scales have the same key signature (share the same notes). The circle of 5ths gives us an easy reference for finding these related keys because the relative minor is inside the circle directly below it's relative major. Notice when play chords how similar a major chord is to it's relative minor. F to Dm, for example or
B to Gm. You can often substitute a relative minor chord for the major. Try playing a song and use an Am in place of a
C, or Dm in place of an F. Because the scales use the same chords, the chord harmonies will still work, although it may give the songs a different feel.