In today’s lesson, we’ll be focusing on the application of the circle of fourths and fifths.

The circle of fourths and fifths is popular among musicians and its importance cannot be denied because it’s used as a reference in a wide spectrum of topics in music.

Let’s discuss briefly on the circle of fourths and fifths before we get on with its application.

## A Short Note On The Circle Of Fourths And Fifths

There are twelve musical notes:

…7 white notes (aka – “naturals”):

…and 5 black notes (aka – “accidentals”):

TheĀ *geometrical* representation of these notes in fourth and fifth intervals produces the circle of fourths. Take a look at all the notes:

…represented in a circle.

It is described as a circle of fourths and fifths because the interval between successive notes in the circle is in fourth and fifth intervals. So, it’s a circle of fourths and circle of fifths as well.

### The Circle Of Fourths – *Explained*

The circle:

…can be considered as fourths in the counter-clockwise direction. For example, from C (on the 12 o’clock position):

… to F (on the 11 o’clock position):

… to Bb (on the 10 o’clock position):

… to Eb (on the 9 o’clock position):

…are all fourth intervals.

### The Circle Of Fifths – *Explained*

The circle:

…can be considered as fifths in the clockwise direction. For example, from C (on the 12 o’clock position):

… to G (on the 1 o’clock position):

… to D (on the 2 o’clock position):

… to A (on the 3 o’clock position):

…are all fifth intervals.

## The Application Of The Circle Of Fourths And Fifths

Beyond learning about the circle of fourths and fifths lies the knowledge of its application.

Although there are several ways to apply the circle of fourths and fifths, we’ll be focusing on two ways it can be applied:

In the determination of

key-signatureIn the determination of

chord progression

Check it out!

### Application #1 – Key Signature

The term *key-signature *is used by music scholars to describe the number of sharps or flats in a given key that distinguishes it from another key.

For example, the key of G major:

…has one sharp (which is F#):

…so, its key-signature is “one sharp”. Also, the key of Eb major:

…has three flats (Eb, Ab, and Bb):

…so, its key-signature is “three flats”.

**Attention:** No two major or minor keys have the same key-signature, hence, every key has its unique key signature.

The circle of fourths and fifths can be used as a reference to determine the key-signature of any given key and I’ll be showing you step-by-step how this works.

In the circle of fourths and fifths:

…the key of C (which is at the 12 o’clock position):

…has no sharp or flat note in its key-signature.

Clockwise from C are sharp keys and counter-clockwise from C are flat keys.

*“Check It Out…”*

Sharp keys include the following keys:

G(one sharp)

D(two sharps)

A(three sharps)

E(four sharps)

B(five sharps)

F#(six sharps)

*“Check Out The Flat Keys As Well…”*

Flat keys include the following keys:

F(one flat)

Bb(two flats)

Eb(three flats)

Ab(four flats)

Db(five flats)

Gb(six flats)

So, a glance at the circle of fourths and fifths:

…shows all the sharp and flat keys.

## Final Words

From what you’ve learned in this lesson, I’m very certain that you’ll use the circle of fourths and fifths as a reference whenever topics like key-signature and chord progression are discussed.

In a subsequent lesson, we’ll be learning how to memorize the circle of fourths and fifths.

That’s all for now!

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