Now that I have explained myself concerning "traditional" music, let's get back to the circle of 5ths.

We generally associate I-IV-V with blues but we find it in classical. Jazz has a number of progressions, one of the simplest and most prevalent is ii-V7. It is also found in other styles of music including folk just as the folk root-5th bass line is found and taught in jazz. ii is in lower case because it is minor while the V is major and so is upper case. What does it refer to?

If we lay out the notes of a scale--say, F major--on a staff in order 1-8, it is F G A Bb C D E F. Now we can make chords of each of these notes simply by stacking 3rds, 5ths and 7ths on top of these "roots." So, the F would have stacked on it ACE and FACE is the F major 7th chord. The G would have BbDF stacked on it and GBbDF is G minor 7th. The A would have CEG and that is an A minor 7th. The Bb would bhave DFA and would be a Bb major 7th. The C would have EGBb and CEGBb is the C7th. The D as a chord becomes a D minor 7th and the E becomes an E minor 7th half-diminished. Right now, it's not important how we determine these chords. Just buy it for now.

So F is I, G is ii, A is iii, Bb is IV, C is V, D is vi and E is vii. It works out that way for any scale--I, ii, iii, IV, V, vi, vii. So in ii-V7, we are interested in G minor 7th and C7th. The ii and the V7 form a very musical relationship. Many songs are written in ii-V7 such as "Satin Doll" and "Getting Some Fun Out of Life."

There are 24 keys to run through and they are arranged in order: D minor 7, G major 7, C minor 7, F major 7, Bb minor 7, Eb major 7, Ab minor 7, Db major 7, F# minor 7, B major 7, E minor 7, A major 7, Eb minor 7, Ab major 7, C# minor 7, F# major 7, B minor 7, E major 7, A minor 7, D major 7, G minor 7, C major 7, F minor 7, Bb major 7 and then ends on Eb.

Now if you look at a circle of 5ths, you'll see that we are following counterclockwise (in 4ths). We skip around a bit after A major 7, we go back to Eb rather than continuing to D but from there we follow the circle all the way until the end. These are all the possible ii-V7s to choose from.

I'll explain a little more about it in a bit but right now I'm dog-tired and need to crash and burn.