The Basics of Music Theory – Part 4 (Cycle Of 4ths)

Now that we have looked at key signatures (see The Basics of Music Theory – Part 3 (Key Signatures)), we are going to delve into the mysterious cycle of 4ths or 5ths depending on which way you see it. It is important and useful to be able to recognize each key and the notes that derive the key quickly. We often place the keys in order. This order is called the cycle of 4ths or 5ths (some also use the term circle due to its diagram as seen below). It is called this because each key proceeds to the next key by the interval of a perfect 4th or 5th depending on the direction (ascending or descending) you are moving.

The Cycle Of 4ths Flat Keys

By looking at the chart below you can follow along with the following explanation. We begin with the key of C major which has no sharps or flats. It is placed at the top of the circle. Moving counter-clockwise the next key is F major. It is a perfect 4th from the key of C major. The notes in F major are F – G – A – Bb – C – D – E. The next key moves another perfect 4th to Bb major. Notice that F major has one flat and Bb major has 2 flats (Bb – C – D – Eb – F – G – A). The cycle continues by the interval of a perfect 4th around the circle until it reaches the very bottom.

The Cycle Of 4ths Sharp Keys

Reaching the bottom you will notice that there are enharmonic beginning at Db/C#. Moving two more perfect 4ths to Cb/B we cross over into the sharp keys. These keys contain sharps and no flats. Because the key of Cb would contain 7 flats, we use its enharmonic of B major to begin the sharp keys. This just makes it easier to work with and also gives an even number to our system. By continuing the movement counter-clockwise, the number of sharps will decrease until reaching the apex of C major.

The Cycle Of 5ths

You have probably noticed the two arrows at the top of the diagram. The left arrow indicates the movement in perfect 4ths and the right arrow indicates the movement in perfect 5ths. Both movements have their place in music theory but most popular music moves by perfect 4ths rather than perfect 5ths.

You might remember from our last discussion on key signatures that each major key has a relative minor. The diagram indicates the major keys on the outside of the circle and the relative minors on the inside of the circle.

Next, we will begin taking a look at chord construction and inversions. If you missed anything from before, then follow this link (The Basics of Music Theory – Part 3 (Key Signatures)) to the previous part of this series. Hopefully, this will be of value to you along with the upcoming exercises to really expand your knowledge of the guitar and music theory. If you are ready for more, then move on to The Basics of Music Theory – Part 5 (Triads and Inversions). In the meantime, to improve your reading skills, you might want to check out my book, Sight Reading Mastery: A resource for all guitarists.

Basic Guitar Theory Scale Primer and Intervals (PDF)

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Category: Music Theory, Supplemental Materials

Interested in going further? Check out Music Theory for Guitarists: Everything You Ever Wanted to Know But Were Afraid to Ask or Alfred’s Essentials of Music Theory: A Complete Self-Study Course for All Musicians. Also, if you are looking for a beginning guitar to apply this theory on, then check out our 10 Best Beginning Acoustic Guitars post.

Chadwick Becks

I have two degrees in guitar performance and was privileged to study under Aaron Shearer, Tom Kikta, David Skantar, Ken Karsh, Tim Bedner, and currently Christopher Berg. Outside my editorial work on this blog, I teach full-time across many genres including classical, jazz, blues, rock, funk, and metal.