Circle Of 4ths and 5ths - Major Scales And Key Signatures

The circle of 4ths and 5ths has many applications when learning music theory. Some of the most useful are knowing how to find out the notes of each Major scale and finding and recognising key signatures for each key.

The term 'key' refers to a starting note, also known as the root or tonic of a chord progression and the term 'key signature' refers to how many sharp or flat notes are in each key. This is then noted on the musical staff so that we can at an instant see in which key we are meant to be playing. But even if you don't want to read music notation it is still useful to understand key signatures.

But first lets find out how to determine the notes of the Major scale in each key. Lets start with the key of C at the 12 o'clock position at the top of the circle of 4ths and 5ths. It is based on the C Major scale which is C, D, E, F, G, A, B. As you can see it has no sharp or flat notes. The next key clockwise along the circle is G (a perfect 5th along from C and also the 5th note of the C Major scale). The G Major scale is G, A, B, C, D, E, F#. As you can see we just start using the same note names as the C Major scale in the same order except for two things: we start with G and make the last note a sharp.

So how do we find the next Major scale? Well the 5th note of the G Major scale is D, so we name the same notes from there on but make the last note sharp, like this: D, E, F#, G, A, B, C#. There are now two sharps in the scale. If you keep going along like this around the circle of 4ths and 5ths you'll add another sharp each time until you get to the key of F#/Gb which contains 6 sharp notes. From here on the convention is to name the notes as flats rather than sharps and you'll find that each key signature has 1 less flat note until you get back to the key of C which has not sharps or flats.

So the key signature that you see on the left side of the musical staff is basically a certain amount of b's (flats) or #'s (sharps). If there are 3 #'s you know it is the key of A. If there are 5 b's then it's the key of Db.

To see what the circle of 4ths and 5ths looks like check out this diagram: circle of 4ths and 5ths. If you want to see just what else you can do with it then download the free e-book "Hit Song Secrets" in which I show you some amazing tricks that include helping you figure out songs by ear or write your own hit songs using the circle of 4ths and 5ths.

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