I just started a learning a little bit of theory and came across circle of fourths. I know that it's basically constructed with a major scale notes that are separated by fourths (don't know if it's the right term). However, I wish to know how this particular layout or the understanding of circle of fourths help me understand things better? More importantly what is the purpose of this? Since I am a theory noob please explain without getting too technical. Thanks.
Eh, things are organized into fifths, which kinda looks the same as fourths, but mean completely different things. Do you know how to calculate intervals? Those are the most important things to learn.
``````
# of Flats (count down fifths)
0 1 2  3  4  5  6  7
C F Bb Eb Ab Db Gb Cb

# of Sharps (count up fifths)
0 1 2 3 4 5 6  7
C G D A E B F# C#
``````

If a song is in G major, going around the circle, you know that there is ONE sharp. The one sharp is one half-step lower than G, or F#.

If a song is in F major, going around the circle, you know that there is ONE flat. The one flat is also the first note of the next flat key, or Bb.

These sharps and flats stack: Db major has Bb (first in F), Eb (first in Bb), Ab (first in Eb), Db (first in Ab), and the new Gb.

If you want to shift to minor instead, move all of these notes down a MINOR THIRD. Two letters to the left and three half-steps down.

Ex:
C (major) -> A (minor)
Db -> Bb

HOWEVER, just because they have the same amount of flats and sharps, they are NOT the same thing. The focus of C major is the note C. The focus of F# minor is F#.

The circle's purpose is twofold:
- in normal music courses, it just shows you keys with the number of flats/sharps and their names
- however, it can be a good reminder of the strength of V-I in tonal music (most of what you hear, particularly in adult contemporary).
The circle of 4ths, also known as the circle of 5ths basically gives you an indication of what key signatures (that would be these, the # which sharpens thus raises a note or the b which flattens or lowers a note, hence why we can call a note a g-flat which would be a Gb [2nd fret on the e-string] or a g-sharp [4th fret on the e-string] which would be a G#) belong to what key and provides a way to figure out which key you're playing in when working with sheetmusic (so not tablature).

The reason of it being known under both names is because they are the same thing, one simply thinks upwards and the other thinks downwards. Many use and know it by the circle of 5ths, but the jazz-guitarist Jody Fisher has published several books where he describes preferring it be named the circle of 4ths, as it is easier for guitarists perception of music compared to their instrument. It is not so difficult, just remember the trick and know the first 7 letters of our alphabet. As a sidenote, you will all have to forgive me if there are minor translation mistakes in this, I know the #(sharp) and b(flat) signs as incidentals, but as far as I know they're to be named key signatures when they're not used as an actual 'incidental', or an exception if you will, so from here on out I'll be calling them that. First off, our 7 notes.

a, b, c, d, e, f, g

From here on, we'll be using them starting at the key of C major, which has neither a # (which raises every note on the line it's placed) or a b (which lowers every note on the line it's placed).

The circle of 4ths can be viewed as follows, first the 7 notes from our starting point...

c, d, e, f, g, a, b

The key of c-maj where we'll be starting has no key signatures and all the 7 notes are plain, but if we use the circle of 4ths/5ths to take a leap 4 steps down (or 5 steps up respectively), we'll wind up at...

1 = c, 2 = d, 3 = e, 4 = f, 5 = g, perfect, the key of G. Going (5 steps up) from the key of C-maj to the key of G-maj, where we'll find that one leap has granted us a key with one key signature, a sharp (#) which is placed at the f making it an f-sharp (or f# if you will). So now our list of notes is...

g, a, b, c, d, e, f#

As you can see we have a new root (The G to be specific, consider it your home-base. It is the focus of your music, the note where you tend to finish and quite often also where you depart from), and one extra key-signature. We are now playing in G (sidenote, I am focusing on the major scales here, ask if you also wish to see the same for the minor scales, as every major scale also coincides perfectly with a minor scale).

Now in sheet music it'll be written down with that sharp-sign (the #) at the line where the f would normally be played, for guitarists commonly the highest of the 5 lines, and it accounts for every f-note in the piece (so long as there are no other incidentals), even the ones that aren't on that particular line, but much higher or lower.

As a perceptive mind you've no doubt seen that when we went up, we took 5 steps, and called it the circle of 5ths, which is in my experience the more commonly applied name. However, if you were to take the circle of 4ths and take those 4 steps the other direction, so downwards, you'd arrive at...

5 = g, 6 = a, 7 = b, 1 = c

...Exactly the same place, so don't fret too much about the name, it just provides you an easier method of defining the key of the piece you're playing, something your ears will probably already have figured out before your eyes should have.

So as you can see, from here on out you can go either direction and for every new leap up or down, you get another key-signature. Something to take into account though, is that it can be confusing when you take either circle and start taking leaps in the wrong direction. Because this is a mathematical approach to music, and a lack of understanding will have you making mistakes as to what key-signature you'll be adding. And if you add the wrong ones, your ears will be telling you one thing, and your mind another (a tip, your ears are rarely wrong). So, to complicate things a little and provide a few examples, and a rule of thumb.

Circle of 4ths, *leaps down - add a sharp (#); leaps up - **add a flat (b). Circle of 5ths, ***leaps down - add a flat (b); leaps up - ****add a sharp (#).

Now the examples to accompany the asterixes.

* The circle of 4ths, a downwards leap 5 = g, 6 = a, 7 = b, 1 = c. Four steps down has us arriving at g, so we'll add a sharp (#), in this case placed at the line of the F, raising the F to an F-sharp (or a F#).

** The circle of 4ths, an upwards leap 1 = c, 2 = d, 3 = e, 4 = f. Four steps up has us arriving at f, so we'll add a flat (b), it is in this case placed at the line of the B, lowering the B down to a b-flat (or a Bb).

*** The circle of 5ths, a downwards leap 4 = f, 5 = g, 6 = a, 7 = b, 1 = c. Five steps down from C has us arriving at f, so we'll add a flat (b), it is in this case placed at the line of the B, lowering the B down to a b-flat (or a Bb).

****The circle of 5ths, an upwards leap 1 = c, 2 = d, 3 = e, 4 = f, 5 = g. Five steps up from C has us arriving at f, so we'll add a sharp (#), in this case placed at the line of the F, raising the F to an F-sharp (or a F#).

As a last note (pardon the pun), this only provides a method for defining what major or minor keys your piece is in. It does not apply to 'fancy', or other non-western scales as those often hold themselves to different intervals. Music by Bartok for example will also use sharps and flats in combination, so remember that this is a method/theory to define a musical concept and perhaps aid in expanding the music you already have (different keys that are linked together by only one leap will not sound as jarring as different keys that require more). Not a rule to limit your imagination, creations or abilities.
Wise Man Says: The guitar is obviously female, she's got hips, breasts... and a hole.
UG's Flamenco Club
Last edited by FretboardToAsh at Jul 13, 2016,
I'm sure I'll get some "feedback" for this, but "the circle of fourths", is merely, "the circle of fifths", played backwards.

The Earth rotates counterclockwise as viewed from the North Pole, and so it goes with the circle of fourths.

Are you guys really going to do pages and pages on this? Never mind, stupid question.
Last edited by Captaincranky at Jul 13, 2016,
Quote by Captaincranky
I'm sure I'll get some "feedback" for this, but "the circle of fourths", is merely, "the circle of fifths", played backwards.

The Earth rotates counterclockwise as viewed from the North Pole, and so it goes with the circle of fourths.

Are you guys really going to do pages and pages on this? Never mind, stupid question.
Of course it is! Hey, we drive on the left in the UK, and go round roundabouts clockwise (if you look from above). And the water goes down the plughole in 4ths....
My own contribution to this excess will follow... (I'm getting a life tomorrow...)
I'm going to try to keep this brief...

The circle of 5ths has two main uses:

1. It's a neat diagram of all 12 keys. The order of keys - the reason it's in 5ths (or 4ths the other way) - is that when a key moves up a 5th, you add one sharp (or subtract one flat). Likewise, when a key moves up a 4th (= down a 5th) you add one flat, or subtract one sharp.
Eg, if you start the C major scale from G (5th note up), you get G A B C D E F G. One note sounds wrong (doesn't fit the formula), which is the F - it needs to be F# to fit the "do re mi fa so la ti do" sound.
If we then start the G major scale from its 5th note (D), the same thing happens: we need to raise the 7th note (C) to get the D major scale; hence 2 sharps. Etc.
Going the other way - starting the C major scale from F (4th up or 5th down) - we get F G A B C D E F. This time it's the B that sounds wrong, and we need to flatten it to Bb. Now if we start the F major scale from its 4th, we start from Bb - and again the 4th (E) needs flattening.
And so on. (It gets a bit messy as we get half-way round, as the flat and sharp keys run into one another, but no need to go there right now...)

2. If you view the letters as chords instead of keys (ignore the outer key signature circle and just focus on the pretty colours), then you get the six main chords in any one key in one quarter segment of the circle.
E.g. if we pick G, then the IV chord (C) is next to it on one side and the V chord (D) is on the other. Inside those three are the three minor chords in G major (Am = ii, Em = vi, Bm = iii). The vii chord (F#dim) is missing, but no one cares about that anyway.
IOW, you can use the circle for composing chord sequences, because chords that are close to one another will sound good together.
You don't have to stick to one bunch of six - you can deviate either way. But the further you go around the circle from your key chord, the more "out" the chords will sound - which is not always a bad thing, of course.

Here's one fun practical application of the circle of 5ths:
https://www.amazon.co.uk/Chord-Wheel-All-Inst-Chart/dp/0634021427
you can get it as an app too:
https://itunes.apple.com/gb/app/the-chord-wheel/id444931977?mt=8
Last edited by jongtr at Jul 14, 2016,
If only you could have taken the time to embolden the preferred enharmonic notation of the Db/C#, F#/Gb, B/Cb, sequence, it would have been perfect..

JUST KIDDING! Really.
Captaincranky
I think you need to take that up with Sienna M. Wood...
Last edited by jongtr at Jul 15, 2016,
jongtr I think I'm getting dote. For the better part of a minute you had me completely stumped as to who the heck was, "Sienna M. Wood".
Last edited by Captaincranky at Jul 15, 2016,