Hey Josh,
As expected, your course has lead me down the road to a greater understanding of music theory and the inter-relationship between roots and fifths. Can you take a moment to explain the chart showing this relationship? I have be able to understand most of it on my own, but I wanted to hear you explain it so that I am not misinterpreting what I am trying to work out on my own.
Thanks, Brian
Hey Brian, thereās a lot of good stuff in thereā¦ how about you tell me what youāve got so far, and Iāll let you know if thereās anything missing or mixed up?
I know this chart relates to diatonic chord progressions. It is suppose to show the complete inter-relationship of musical notes and intervals. If I am reading this correctly, if you move clockwise, the circle rotates in 5ths (V) ie: the 5th (V) of the C is G. If you move counterclockwise, we are moving in the direction of 4ths (IVth) ie: the I4th (Vth) of a C is an F. The same is true for the minor scale shown below. The inner minor circle seems to link the Major key to the 6th (vi) ie in the key of C the 6th (vi) is a Am and so on. Now this is where things get a little funky. If I move from the C, down diagonally to the left, I get a ii or Dm. Likewise, if I move down from the C to the right, I get the Em or iii. If any of this is true, (and it seems to be) there is a lot more here than just a ācircle of fifthsā. Also, I donāt know what role the diminished seventh plays in all of this.
I love your course, and have reviewed some of the lessons several times. However, because I had a musical background, I seem to want to take your course material and run with it. I stumbled on the Circle of Fifths sometime ago after finishing your module on fifths., thirds and sevenths. I am just now trying to wrap my head around this. Any help or suggestions you have would be greatly appreciated. Maybe this would make a great course topic?
Thanks,
Brian
Yep, thatās all dead on.
I suppose you could try to glean data about diatonic chord progression here, but this is more about keys than chords. Thatās why thereās no diminished seventh chord anywhere - the major/minor designations arenāt talking about chords (primarily at least).
The only big thing thatās missing from our discussion so far is the helpful role this chart can play in remembering key signatures -which are missing from this version of the chart. Hereās one with more data (and more colors 
)
So important tidbits here:
You can also see how different interval movements will affect key signature. For example, if you skip one key and go from C to D, which is a whole step, you add two sharps (or if you jump back to Bb, you get two flats). So you can file that away and know that any time a song modulates up a whole step, for example, there will be two notes that change from the previous key.
@Gio, anything to add? Curious if you ever use the circle to talk about chord progressions like Brian was talking about, Iād actually never heard of it being used like that.
This is a terrific help. There seems to be a lot here to work with. Thanks for all your help.
I havenāt used the circle to talk about chord progressions the way you were with the ii and iii chord, @bsickels. The chord progression magic happens when you watch root movement around the circle of fourths (or, as the classical cats call it, falling fifths) - but it isnāt key signature or chord quality relevant - itās only root relationships.
(as in iii-vi-ii-V-I ā¦ in whatever key, itās moving in fourths the entire time, the chord quality changing to fit the key youāre in)
The closeness of the ii and iii seems like happy coincidence. If itās helpful, awesome. But I donāt think it fits in to much application or practice that Iāve run across.
I second that.
The bass on this killer. My dream is to be fluent in this MoTown soundā¦
He is the man!
Older post, but Iāll add to this instead of creating a new one. I found this video helpful in me understanding the circle of fifths. I think itās aimed at kids though so it can be a bit patronizing. 
And this one is a more advanced video that covers chord creation and such:
I did this sketch to try and illustrate a little better how the circle of fifths works.
Unfortunately it hasnāt scanned too well, but hopefully it will still help anbody who is struggling to get their head around it.
As an example, if you take the C scale in the illustration, and then look at the F scale and G scale on the inner ring, you can see that the first 4 notes of the C major scale are the last 4 notes of the F major scale, and the last 4 notes of the C major scale are the first 4 notes of the G major scale.
Also notice that if you pick any of the major scales (on the inner or outer ring) both of itās linked scales only have 1 note that is different.
Using C again as an example, F major scale has B flat and G major scale has F sharp.
This applies to each and every major scale - the scale next to it in either direction only has 1 note that is different. That is why they are the next scale. They are most harmonious, because they are almost identical, because all except for 1 of the notes are the same.
The lightbulb moment for me, was in understanding that the keys overlap starting, from the fifth note, in this way.
Very cool to dig into this like you do! And there is something awesome in exploring the āsymmetriesā here and the mathematical connection between geometry and harmony.
I guess this is another way of saying āas you move away from C, either clockwise or counterclockwise, the key signatures incrementally acquire one more sharp of flat, respectivelyā
I think I know what you mean, but saying āmost harmoniousā is also a bit fuzzy hereā¦ It is probably partly because you shouldnāt compare the scales, but the chords derived from one scale! So, if you center everything around C for starters, and then look at the chords derived from the C major scale, then you find that, indeed, the F major chord is there and the G major chord is there, but NOT the D major chord, Bb major chord etc. That is because the latter are not diatonically related to the C major scale, whereas the former are.
There is so much to explore and understand - your epiphany about the āoverlappingā scales is pretty cool though 
Thanks for your posts, @JT and @Mark_D . . . 
Gave me a little more insight and understanding.
Cheers, Joe
No it isnāt. Not at all. If one is playing a simple 3 chord song and the the key chord is āCā, then the most likely next chord will either be an āFā or a āGā - because they are the most harmonious, because they are built from a scale that has the most similar group of notes, and they are linked by 5thās in either direction.
You could go on to argue all you want about relative minor keys, and 2/5/1 progressions etc, but if you could bet on it at the gambling shop (which would be the next most likely chord played after āCā) then the clear winners more often times than not, would be F and G - and most likely in that order.
Ditto for any other chord/scale around the circle.
Incidentally, if you were in fact playing in the relative minor key of A minor, then the safest bets at the gambling shop for most likely next chord, would be D minor and E minor. In that order, and for the exact same reasons.
Epiphany lol - nice word for it, but thatās the main point. They do overlap - from the 5th note. Hence why it is called The Circle of Fifths.
Other pictures of the circle of fifths donāt illustrate in the same way - thatās why I drew the picture as soon as I understood what was going on.
Itās just a shame the blue I used on the inner ring doesnāt show up very well.
Iām also all for simplicity, and that is the simplest pictorial representation I can think of.
Vox made a super great video on this topic
Me tooā¦ā¦.my fave Bassist James Jamerson.
Want a challenge?
Create a your own circle of 5ths by hand.
I do this every now and again just to keep the little grey cells active.
Here is a starter sheet I put together to get you started.
With the notes at the bottom of the sheet you should be able to figure it out.
Here is what the completed sheet should look like.
I keep adding notes but you get to the point where it turns into more than one sheet.
There is more to the circle of 5ths than meets the eye. For instance you can pull out the most harmonious chord groupings in a song (I IV V) in an instant.
Check out this video about playing most pop songs with only 4 chords (I, IV, V, vi)
https://www.youtube.com/watch?v=5pidokakU4I
I hope this post helps some that may be struggling with the circle of 5ths/4ths.
Nice practice idea.
I love Axis of Awesome. I play that song every now and then, because I just like it apart from the message, taking the piss out of the pop industry.
I cannot count the number of times I have used this chart over the years.
Everything from scales to chords to chord progressions and inversions etc. etc. etc.
Initially I made the chart over 30 years ago because once you get into the reaIm of 5 6 and 7 sharps, and flats, most charts do not show all of the key signature names. As a matter of fact the chart Josh posted is the only one I have seen recently that also shows them all. Even the OP chart does not show all of them.
Regarding this topic, I found this page/tool very interesting:
https://randscullard.com/CircleOfFifths/
