Circle of Fifths

The circle of fifths is the relationship among the 12 tones of the chromatic scale, their corresponding key signatures, and the associated major and minor keys. Looking at the circle:

the outer section shows the actual key signatures
the capital letters represent the corresponding major keys
the lowercase letters represent the corresponding minor keys

The reason it’s called the circle of fifths is because of the interval relationships between each key signature. Key signatures can get a little tricky to remember, so the circle of fifths is a great tool. Let’s look at how the key signatures coordinate with the circle of fifths below:

C Major and A Minor have no sharps and no flats
G Major and E Minor have 1 sharp
D Major and B Minor have 2 sharps
A Major and F# Minor have 3 sharps and so on…

Use the circle of fifths to recall how many sharps or flats each key signature has, and to understand which major and minor keys are relative (or share the same key signature). For example: C Major and A Minor.

Applying The Circle:

The circle of fifths is regularly used for strong bass line movement, which in turn leads to some great chord progressions! A very common bass line movement is: Up a 5th, Down a 4th.

At first glance, it might not seem like this progression is following the circle of fifths because not every interval is an ascending 5th, but when you pick out the notes you will see: C, G, D, A, E, and B. Add some right hand notation, and you have a nice little melody using the circle of fifths as your structure!
Using the circle of fifths makes modulating from one key to another much easier! That’s because the keys to the left and right of the key you’re in are all considered the best options when modulating.

Let’s use C Major as an example:
- The keys to left and right of C Major on the circle are F Major and G Major.
- These keys are the best keys to modulate to because of the chords they share with C Major.
  
  The circle of fifths is a great tool for showing you which keys share chords and are best for modulation purposes.
- C Major and G Major
  - Chords in C Major: C, d, e, F, G, a, b diminished
  - Chords in G Major: G, a, b, C, D, e, f# diminished
- C Major and F Major
  - Chords in C Major: C, d, e, F, G, a, b diminished
  - Chords in F Major: F, g, a, B♭, C, d, e dim

When modulating, you would likely use one of the shared chords to modulate to the new key.