This brief article introduces and explains Cycle of 4ths chord progressions. It also explains why such progressions are challenging for beginning improvisationalists. To illustrate I've chosen the country song Blue by Bill Mack Smith, as recorded by LeAnn Rimes. To follow along you'll need a basic understanding of scale numbering, chord numbering, and chord formulas, however I'll include some refreshers and introductory concepts regarding those matters.
Here's a link if you just what to see the chord chart for Blue in Roman numbering.
A cycle of 4ths chord progression is usually a progression of dominant 7 chords (chords with the formula 1, 3, 5, b7) which ultimately resolve to the root of the key with a Major, Major 6, or Major 7 chord. may include dominant 7 chords, major chords, or a mixture of the two.
The term "dominant" has multiple meanings in music. Since Dominant chords are often core to the concept of Cycle of 4ths, let's look look at the meanings:
That's pretty much what you need to know about dominant chords. So on we go!
The Cycle of 4ths chord progression runs throughout the song Blue. The verse starts on the I chord, then jumps to the III dominant chord, and from that point it's a cascade of dominant chords progressing in ascending 4ths, eventually resolving to the I chord.
Here are the verse's chords written in Roman numbering. Note that the "pipe character" | is not a I chord. It’s an indication to hold the previous chord for an additional measure:
I III7 VI7 | II7 V7 I |
As shown next, Blue's chorus is a pure cycle of 4ths and perfectly illustrates this progression which is heard often in classical music, jazz, swing, blues, country, send practically in every style. It starts on the III (the point where the 4ths progression begins) and resolves to the I:
III VI II V I <-- Roman Numbering
For clarity I removed the "measure marks" and I removed each "7" ... which indicate the Dominant 7 chord type.
Note that the I chord doesn't appear at the end of the chorus, but occurs as first chord of the following verse. That's the point where the cycle is fully resolved.
Here's the chorus Cycle of 4ths again, however beneath each Roman numeral I've added Arabic numeral chord numbering—this system is sometimes loosely called Nashville Numbering. Once again, for clarity, I've removed the 7s.
III VI II V I <-- Roman Numbering
3 6 2 5 1 <-- Arabic or Nashville Numbering
So there it is, clear as can be, the chorus of Blue moving through a 3-6-2-5-1 chord progression. A hugely important and widely used progression.
A bit later I'll illustrate the relationship between the Cycle of 5ths and the Cycle of 4ths, which is simply the difference between moving clockwise or counter-clockwise around the Cycle of 5ths.
Cycle of 4ths progressions can be long or short! The longest is usually a sequence of five chords starting on the III.
Here are some examples:
III7 VI7 II7 V7 I <—- usually the longest (used throughout Blue) VI7 II7 V7 I <—- more common II7 V7 I <—- extremely common V7 I <—- not usually considered a cycle, but it is!
But you may ask, "What makes this a cycle of 4ths progression?" Cycle of 4ths exists when each chord is a 4th "higher" than the the prior. That doesn't necessarily mean that each chord tone is a 4th higher, it's just that when you count up four degrees from each chord root you find the next chord's root. (Once the chord root and type are known, you can choose the octave for the root, and voice the chord as you wish.)
Counting 4ths sounds simple enough, but let's cover the concept of counting intervals and look at the common off-by-one goof.
When counting intervals it's easy to miss by one letter name. So, heads up. Many people count musical intervals incorrectly and get an "off-by-one" error, so I strongly recommend that you read this short article that discusses "off-by-one" errors.
Another issue is missing by an accidental—you get the right letter name, but you miss the correct pitch by one half-step. For instance, you get an F instead of F#.
There are only seven letter names in the musical alphabet, so when counting up through the musical alphabet, we go from A to G. Upon reaching G we start over at A and continue from there. Each time we reach A we're in another octave, sometimes referred to as a pitch class.
Let's give it a try. A 5th higher than E is counted E F G A B <—importantly we include E and count it as the 1st degree. Many find it helpful to say the letters while counting on your fingers:
E F G A B
1st 2nd 3rd 4th 5th
Accordingly there are just seven numbers in chord numbering systems. So when we reach 7 we start over at 1.
For instance, a 4th higher than a 6 chord is counted: 6 7 1 2. Importantly we include out starting point of 6. The answer is: 2 chord is a 4th higher than a 6 chord.
For simplicity (and to avoid chord roots with accidentals) let's look at Blue's chorus in the key of C.
As previously stated, the chorus's chord progression is:
3 6 2 5 1
In the key of C the I chord is C. And the chorus starts on the III Chord. To find the III chord we count up three letters, importantly starting at C and inclusive of C. In other words we count "C D E" as 1 2 3, thereby determining that the III chord is E. (If you calculated F read about "off-by-one" errors?)
In the key of C, Blue's chorus starts on E ... and it's the 3 chord: E 3 Next we count up a 4th from E: E F G A In doing so we determine that A is a 4th above E. Just as we counted from E up to A, now we numerically count up a 4th from 3: 3 4 5 6 This means A is the 6 chord in the key of C, so we add that to our list of chords E A 3 6 We continue the process(counting up 4ths) until we reach the I chord. We count up a 4th from A: A B C D And count up a 4th from 6: 6 7 1 2 We find that the 2 chord in C is D, and add it to the end of our list: E A D 3 6 2 Continuing our way through the cycle: Count up a 4th from D: D E F G And count up a 4th from 2: 2 3 4 5 We've determined that the 5 chord in the key of C is G, add add it to our list E A D G 3 6 2 5 And here's the last step of the cycle: Count up a 4th from G: G A B C And count up a 4th from 2: 5 6 7 1 We've reach the 1 chord and that completes the Cycle of 4ths: E A D G C 3 6 2 5 1
Except for the I and V all the other chords have notes outside the G scale, so when improvising you'll need to switch to a scale that fits each chord. For this style of music a relative blues ( 1, 2 ,b3, 3, 5, 6, optional b7) or blues scale (1, b3, 4, b5, 5, b7) built on the root of each chord works well, but there are lots of tricks. One of my favorites is focusing on descending tritones, the tritone at the center of each dominant chord.
You can study the blues and relative blues scales for guitar here. They're initially shown in A, but you can easily set the root to any key. And you can choose an instrument other than guitar. For instance, here are the same scales but for violin, fiddle, mandolin, and other instruments tuned in 5ths.
It’s kind of odd that the G scale sounds bad over a long held D chord (because the G scale contains D F# and A, the notes of the D chord.) But the F# is the 7th degree of G, and the A is the 2nd degree, and both are dissonant and therefore unstable. I'll have to think about it more; I just know that the tonic scale starts to sound mismatched when the V is held for a measure or more, and it's a definite mismatch over the III, VI and II chords.
I III7 VI7 | Blue oo oo oo oo oh so lonesome for you II7 V7 I |(V7) Why can't you be blue over me I III7 VI7 | Blue oo oo oo oo oh so lonesome for you II7 V7 I - IV I Tears fill my eyes ‘til I can't see III7 | VI7 | Three o'clock in the morning here am I II7 | V7 | Sitting here so lonely so lonesome I could cry I III7 VI7 | Blue oo oo oo oo oh so lonesome for you II7 V7 I | Why can't you be blue over me Solo: I III7 VI7 | II7 V7 I | III7 | VI7 | Now that's it over I realized II7 | Those love words you whispered V7 | Were nothing but lies ( -- Optional key change up one half step -- ) I III7 VI7 Blue oo oo oo oo oh so lonesome for you II7 V7 I Why can't you be blue over me II7 V7 I Why can’t you be blue over me
Capo 2 for the key of A which is the key Rimes sings it in, until she goes up a half step near the end.
G B7 E7 | Blue oo oo oo oo oh so lonesome for you A7 D7 G |(D7) Why can't you be blue over me G B7 E7 | Blue oo oo oo oo oh so lonesome for you A7 D7 G - C G Tears fill my eyes ‘til I can't see B7 | E7 | Three o'clock in the morning here am I A7 | D7 | Sitting here so lonely so lonesome I could cry G B7 E7 | Blue oo oo oo oo oh so lonesome for you A7 D7 G | Why can't you be blue over me Solo: G B7 E7 | A7 D7 G | B7 | E7 | Now that's it over I realized A7 | Those love words you whispered D7 | Were nothing but lies ( -- Optional key change up one half step -- ) G B7 E7 Blue oo oo oo oo oh so lonesome for you A7 D7 G Why can't you be blue over me A7 D7 G Why can't you be blue over me
This is the "concert" key that Rimes sings it in, until she goes to Bb near the end.Folk style guitarists can readily see that playing in the key of G capo 2 simplifies matters. Guitarists using closed-fingering jazz chords won't bat an eye at the key of A for this song.
A C#7 F#7 | Blue oo oo oo oo oh so lonesome for you B7 E7 A |(E7) Why can't you be blue over me A C#7 F#7 | Blue oo oo oo oo oh so lonesome for you B7 E7 A - D A Tears fill my eyes ‘til I can't see C#7 | F#7 | Three o'clock in the morning here am I B7 | E7 | Sitting here so lonely so lonesome I could cry A C#7 F#7 | Blue oo oo oo oo oh so lonesome for you B7 E7 A | Why can't you be blue over me Solo: A C#7 F#7 | B7 E7 A | C#7 | F#7 | Now that's it over I realized B7 | Those love words you whispered E7 | Were nothing but lies ( -- Optional key change up one half step -- ) A C#7 F#7 Blue oo oo oo oo oh so lonesome for you B7 E7 A Why can't you be blue over me B7 E7 A Why can't you be blue over me
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