Now, I am by no means a expert, I use the Circle of Fifths very much in a layman type way BUT I've found it to be very helpful. Here's how I use it. For a far more technical and thorough explanation visit www.circleoffifths.com as it's a fantastic resource for music theory.
The Circle Of Fifths is used for a number of things:
1. Describes the relationship between the tones (or pitches / notes) of the chromatic scale
2. Gives us the key signatures of any given major or minor scale (i.e the number of Flats or Sharps in that scale)
2. Shows us the associated relative minor key to any given major key.
Wtf!?
It will become clearer.
As you travel clockwise around the circle of fifths you move in intervals of a perfect 5th. The interval between C & G is a perfect 5. The interval between G & D is a perfect 5th and so on -
Using the Circles of Fifths one can determine what key signatures sound similar, in that, keys located next to or close to each other on the Circle sound similar because they share almost the exact same notes.
An example is the key of C major (which has no sharps or flats) and the key of G which has almost the exact same notes except G has 1 lonely sharp and that just happens to be F# - so instead of playing F we play F# - that's the only difference between C & G major. Trippy.
As we move clockwise from C around the Circle of Fifths we add sharps. C has zero sharps (or flats), G has 1 sharp, D has 2 sharps, A has 3 sharps, and so on around the Circle. Also, it's handy to note that the sharps accumulate as you move around the Circle - once you've added F# you always have F# as the first sharp in any key signature - when you get the key of D major (i.e two sharps) we start with F# and then we just move around the Circle clockwise from F (i.e to C) and thus the Key of D has an F# and a C# and so on around the circle. You see it's all about the circle.
The Circle of Fifths also shows us the relative minor key to any given major key. For example, the relative minor of C major is A minor - what this means is that these two keys share the exact same notes but sound distinctly different. This is due to how our ear hears a scale given what we perceive to be the root note - in C our ear perceive C to the lowest or root note of the scale and as we ascend up the scale it feels happy due to the mysterious pattern on of wholes steps (W) vs half steps (H) up the scale.
What is a whole step and what is a half step? Good question!
The piano is laid out in half steps - any note beside each other, regardless of color is a half step but I've always remembered it like this...If two white notes have a black note between them, it’s a whole step. If two white notes have no black note between then it's a half step. As such the all-important pattern of C major can be expressed as:
W W H W W W H - This pattern is the same for any major scale!
Although the key of A minor has the exact same notes as C major the crucial difference is we start the scale at ‘A’ and as we ascend it sounds vastly different (sad) because the pattern of whole steps vs half steps has changed due to the freaky way the western world lays out their keyboard.
W H W W H W W - This pattern is the same for any (natural) minor scale.
O.k - that's some heavy stuff but how is knowing the Circle Of Fifths useful even if you don’t play the piano? Maybe you just make beats?
Here’s one example.
Let’s say you download a really cool loop from https://splice.com/ and it happens to be in A minor - you love it but you only have this one loop and you don’t know where to go for the chorus or the bridge etc. Well, you could always download another loop in A minor but majorly obvious!
Knowing that A minor is a relative minor to C major is very useful and gives you options to smash a C major loop in front of it or after your sad little A minor loop depending on how you want it to feel.
Boom.
Thanks, music theory and thank you Circle of Fifths!