What Is the Cycle of Fourths / Cycle of Fifths?

Once you nail this mysterious circle of roman numerals, a world of harmonic patterns will quickly come into focus

A long time ago in a suburb far far away, I was sitting in the basement of my guitar teacher’s house, eyes glossed over, staring at a piece of paper that was titled “Cycle of Fourths / Cycle of Fifths”. Although I was nodding and uttering flat out lies such as “yep, got it… sure, I understand….”, I was also wishing that I was instead at the dentist or having lunch with an insurance sales-person.

What a shame, that guy was a great teacher and I was a moron. I just could not get it. What does this cycle do?, how does it affect me and my ability to meet girls? Y’know, the kind of thinking that is common for a 16 year old kid who clearly has his priorities in order. I wanted to grasp the significance of this mysterious circle with “IV” and “V” written like the face of a busy early Roman clock, but at the same time, I was wondering if he might help further my cause with more speed by just teaching me how to play mindlessly fast and flashy runs. Fortunately, my teacher was a very wise man who always resisted the temptation to just fill my head with crap; he actually tried to help me grasp theory and get me to understand how vital it was to being a solid musician first, great guitar player second.

Ughhh… all right, I’ll eat it, but I’ll hold my nose.

Many years later, I look back on that experience and wish that I could have just used my noggen a bit more and listened to this guy. Sure I did my homework, but I also spent as much time working on mindlessly fast runs. What I fortunately came to realize is that understanding such relationships as the Cycle of Fourths and Cycle of Fifths is not only doable, it opens up a world of clarity with regards to patterns in music and how they really get you tuned in to what you are doing.

Short Answer: The entire guitar is tuned in fourths… it’s almost that simple

A short while after the fore mentioned scenario, I was sitting alone in my room late one night, black and white TV in the background with some odd UHF station only half coming in right. It was probably “The Honeymooners” in Spanish. I was staring at the neck of my cheapo Univox Les Paul Jr. copy, probably smoking one of my first ciggarettes and trying to grasp this deep circle of mystery when it suddenly dawned on me: “hmmm, whatever

note I play on the low “E” string, a fourth above that note is the same fret, one string up…  wait, it’s the same thing with the “A” string… the “D” string.. wait, the “G” string too… ok, so the guitar is tuned in fourths. Wow that is really simple. Uh… wait, the interval between any note on the “G” string and the same fret on the “B” string is not a fourth, it’s a…uh..mmm…’one, two…er…three…’..ok, it’s a major third… got it.

Updated Short Answer: The entire guitar is tuned in fourths, with the exception of the relationship between the “G” string and the “B” string, that interval is a major third

But what is this “Cycle of Fourths?”. Well, as you can see this example, if you play an “A” note on the low “E” string (5th fret), and then play a “D” note on the “A” string (5th fret), you have moved up a fourth. Then play a “”G” note on the “D” string (5th fret), you have moved up a fourth again, keep doing this over and over (compensating for the exception of a half step lower interval between the “G” and “B” string) and at some point, actually on your 12th iteration, you will find yourself back at your original note of “A” (granted in a higher octave, but we are concentrating on just the theory here). So, this cycle is simply another way of saying that when you play a note, play a fourth up, and then a fourth up from that note, etc, you eventually wind up playing your original note again. It doesn’t matter which note you start on, this exorcise works the same every time. This is why it is called a “Cycle”, it is a process that never ends, as you keep playing a fourth up, you wind up repeating the same note every 12th step.

Well, then what about the Cycle of Fifths? Same drill. Just try the above example moving up a Fifth each time instead of a Fourth. On the guitar, a Fifth up is the next string up, two frets up. If you play an “A” note on the low “E” string, a Fifth up is the “E” note on the “A” string (7th fret), and so on.

“OK, so how does this affect me?”

The first real benefit to this is realizing that for example, a Blues is not “A” and then “D” and then “E”. If you think in this way, then when a band plays a Blues in another key, you have to think:  “OK, so this Blues song is “G” and then “C” and then “D”… There is a more efficient way to approach this. Instead of thinking of the actual chords, think of the scale degrees that those chords are based on. If you do, then you will realize that a Blues can often be described as a “I” and then a “IV” and then a “V”. When a band calls out a Blues in a different key, you won’t have to worry about what the actual chords are, just ask yourself what a “I” a “IV” and a “V” chord is in that key. If someone says “This next song is a minor blues in C, but the turnaround is “V7-#V7-V-I…” you will be ready for action.

This may seem like baby stuff, but it really starts to pay off when you need to play a cover song in a different key. I got caught off guard one night on stage with “Knock on Wood”. I was so used to playing that song in “E” and I know that the very first chord of the intro is a “D” and then a “B” and then “A” and then “G”. One night, a singer called it out in the key of “D”. I immediately became disoriented. “Ahhh crap! what the hell is the first chord if the song is in “D”??…. wait, when it is in “E”, the first chord is a “D” chord, so in they key of “D”, the first chord is “C”…ok…. but what is the second chord?….” and so on. Later that night I was sitting in my hotel room, soaking my bruised ego in a big bucket of ice water when I decided that there had to be a better way to be able to transpose such a simple song on the fly. I just visualized the chord numbers and the interval relationship between them and “Poof!” it was done. Intro: “VII-b” – “V” – IV” “III-b” – “I” Finito. I was ready to play that song in any key.

Granted, “Knock on Wood” is not exactly on the same level harmonically as “West Coast Blues” or “Take Five”, but I use that one as an example because while the rest of the song is very easy and fairly diatonic, the intro can catch you off guard if someone calls it out in a different key because the very first chord of the song is a flatted VII chord, not the tonic.

Ok Kevin, where exactly are we going with all this?

Once you have the whole Cycle of Fourths / Cycle of Fifths thing down, you will start to see other patterns specific to the fretboard that are littered all over the neck. Even as you solo, the less you think of the actual notes you are playing and instead the relationships between them, the more you can sculpt the sound of a solo, not just repeating patterns that you have learned. This becomes even more apparent when you are playing “Out” notes. I used to think of “Eb” as a note that simply “Never belonged in the key of A major” Nonsense. Eb belongs in A Major as much as any note in the universe. No, it is not one of the diatonic notes of the scale and most often it sounds pretty crummy when played on a strong beat against just any old chord. But as a leading tone or passing tone, “Eb” is a very useful tool. Would I use a fatted fifth (or raised fourth) when playing a John Cougar Mellancamp cover?… uh, no, probably not. But what about a minor blues? Absolutely. Depending on how and when you play it, that note can be killer.

This was yet another one of my long answers to a short question. But while a short answer might have sufficed, a slightly in-depth review of this topic can really broaden your horizons. After 30 years, I am still discovering fun patterns all over the fretboard, and that is in standard tuning. Imagine the exponential growth of possibilities if you throw in alternate tunings?

First get the Cycle of Fourths / Cycle of Fifths down cold. Once you do, lots of other really fun and helpful concepts will start to fall into place without as much head-scratching.