Just wondering about subs for vi-7 and ii. I assume they work like subs for V but there's probably some tricks I don't know.

I ask because I'm working on a solo arrangement of Stomping at the Savoy and the first ending is boring.

Db6 Bb-7, Eb-7 Ab7. (Really an Ab13 because if the melody)

Never heard that before. When I was messing with it I realized that I'm pretty familiar with fun stuff I can do with I and V chords but don't have a lot of things to do with vi and ii chords. I'm pretty sure the same kind of things apply but maybe not.

Obvious ones Bb7 Eb-7 Ab13, E7 Eb-7 Ab13, E-7b5 Eb-7 Ab13

The one I like the best atm is Db6 Bb-11, A7 Ab13 because it walks up to the 13.
Db Eb E F and walks down to the Ab.

So idk, maybe you cats have got something.

And who the hell wrote the bridge for Stomping at the Savoy? You have this sweet melody and then BAM. Shitty chromatics and a dom cycle. Did they even try? The A section makes up for it though.
It is the exact same principle as V chords. You can substitute in any chord with similar function, as well as dominants of the target chord. You even have a little more free reign here because there's no melody in the turn around.

When you are working it out, stick to 7th chords and quality. Extensions are always negotiable.

Db6 Bb-7 Eb-7 Ab7 = lame

F7 Bb7 Eb7 Ab7 = All Dominants?

B7 Bb7 A7 Ab7 = All tritone subs

Db6(F7 or B7) E7 A7 D7 = All dominants off tritone sub

F7 E7 Eb7 D7 = All Tritone subs off sub

Dbmaj7 - Emaj7 - Amaj7 - Dmaj7 - Constant structure maj7th mediants.

Fm7 - Dbmaj7 - Gbmaj7 - Gbmaj7#11 - Same functions, different roots.

That's just to get you started, all those can work if you make combinations too.

You see where I'm going with this Duane. Keep this in mind.

Any chord can be preceded by its dominant. Or its SubV.

I'll come up with more later. Obviously this barely scratches the surface.
"There are two styles of music. Good music and bad music." -Duke Ellington

"If you really think about it, the guitar is a pointless instrument." - Robert Fripp