I typically try to figure out chord progressins by the bass movement and the chords, but these, I really don't know whats happening. Can you explain it a little...key....movement....etc...
Hey MrAndrew, I've just seen this arrangement & can't wait to try it out.
I understand exactly what you have done because I do it all the time in my practice time
4HG, coming up with this type of progression requires you too change or rather broaden your thought process a bit/ revolutionise the way you think of chords with bass notes.
What do I mean by this?
As you can see, MrAndrew said this was a jazzy progression.
There are chords that have a very jazzy "cut" / "fit"..
If you want to play jazzy, you need to be able to identify those primary chords.
For instance, the 1st chord that MrAndrew used was a Gm9 [G/F-A-Bb-D]. I would advise that you learn this chord using the chromatic scale & then learn the different inversions for the RH notes.
ok, enough of that blabber.
I think what's important here is the thought process:
This is what I think MrAndrew did (at least it's what I would do).
i) Think of a certain feel you want to create.
ii) This works best when you have a bank of chords in your pocket. So you already have an idea of which chords will flow together.
iii) You don't want to sound too normal (which is what normally happens when you just move in 4ths all the time)..hence the reason MrAndrew has sometimes "broken" the 4ths pattern.
(but then at some point even though you've abandoned the 4ths cycle, you need to get back to it or some other pattern , hence the reason MrAndrew goes with the pattern here & there.
The most important thing is to be guided by the sound you hear in your head rather than going with the pattern in the bass notes. In that way we don't limit our imagination's creativity 
Indeed by just looking at it I am guessing it's in Ab. 
