Music Theory – Understanding the Circle of Fifths

This will be the first of my posts on music theory to helping any of you budding musicians out there.

The circle of fifths is a well presented way of seeing the relationship between keys, how to work out number of sharps or flats, how to work out relative minor keys and also see the relationship between the tonic and the dominant.

But let’s slow down a bit and get the basics out of the way.

In the same way that every lock has a specific key with specific ridges on it, most of the pieces or songs we listen to have a key – a set of accidentals (sharps or flats) and alter the scale to make them our standard western major or minor. In every major scale, for example, the notes are always divided up with the same pattern to create the list of notes we know. This is made up of tones (a tone is like two little steps on the piano, e.g. C to D) and semitones (one little step, e.g. C to C♯/D). The order in a major scale goes like this, represented by T (tone) and S (semitone):

T  T  S  T  T  T  S

In the context of C major, it would look like this:

C  D  E  F  G  A  B  C

T   T   S   T   T   T   S

Note that C major has one of the five letters of the alphabet represented, A-G. This is apparent in every scale of this style: major or minor. When we apply this to the strongest related keys to C major, we have to make adjustments to keep the spacing the same and preserve the sound of the major scale.

C  D  E  F  G  A  B  C

G  A  B  C  D  E  F G

T   T   S   T   T   T   S

G major has only one accidental, and is one of the strongest relations to C major. In the scale, every pitch has a name that relates to its position. The first note is the Tonic and the fifth note is the Dominant. Therefore, G is the dominant in the key of C. Here is a list of the name of each degree of the scale in C. The numbers represent the number of the scale and if the chord is minor by being lower case:

C                Dm              Em                   F                  G                Am            Bdim

I                    ii                 iii                    IV                  V                 vi               vii°

Tonic   Super Tonic   Mediant   Subdominant   Dominant   Submediant   Leading Note

In the circle of fifths, it is presented as one accidental is added at a time. From C major, we go to G major. From G major we go to D major, and so on until we reach C♯ major. The same goes anti clockwise for the flats: C goes to F, the subdominant which also only has one accidental, B♭.


Each key also has a relative minor key, one that starts a minor third (3 semitones) below the major key and with the same key signature.

For example, as seen on the circle, the relative minor of C major is A minor. There are different types of minor (harmonic, melodic, etc.) but this is it in its simplest form.

The order of tone and semitones in these minor scales are as follows:

T  S  T  T  T  S  T

In the context of A minor, it looks like this:

A  B  C  D  E  F  G  A

T   S   T   T   T   S   T

You may have also noticed that each major key represented in the circle has a corresponding minor key – a key that sounds ‘sad’ and has the same amount of sharps and flats as its relative major key. If you like to live dangerously, you can find the relative minor from its major by going down a minor third (a tone and a semitone). In E Major, this would take you to C minor. As E Major has 3 flats, so does C minor. If you have a good memory, it’s a better idea just to memorise as many as you can and then work the rest out from there. For example, if I memorise that C minor is the relative minor of E Major, I can then quickly work out that the relative minor of E major is C ♯ minor, or the relative minor of D Major is B minor, because they are only a semitone away from the one I originally remembered.

As a tutor of music theory, I often get asked about quick ways to remember on how to work out what key it is from the sharps and flats, so here is my little music hack:

  • If a key has flats, it is simply the second to last flat that is the answer. If you see 2 flats in a key signature (B♭and E♭) then the key will be B♭.
  • If a key has sharps, go up one semitone from the last sharp. This last accidental is the leading note to the Major key, so if it has an F♯ in the key signature, then you know it is probably in G major.

However, we also know that G major has the same number of sharps as its relative minor: E minor, so we look at the notes used in the music. The first bar of the main melody will often give you the answer, and the clue is usually in the bass. If you see F♯ in the score but an E in the bass, you can suspect that it may be E minor. To check further, read the other notes of the bar – if they spell out an E minor chord (E G B), then you know it’s in E minor. If you see some accidentals, particularly like D♯, this is another clue that the key is probably minor as D♯ is the leading note for E. 

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