This is the last chord of the sequence, and when practicing over the Part 4. Backing, start out by playing the tried and true A Whole-Half diminished. Treat A as the root, or "home-base", but also try to play the same scale, but treating Ab as root. See if you can switch between these "modes" of perception back and forth. Head over to the backing track and try it out.
Once you're back, listen to the outro improvisation. Over this track I have laid down a bass line as well, to keep a more solid key to play over. However, I try to as much as possible play only by ear in this clip, trying not to let my fingers or theory guide my note choice, but just reaching out there, and when I land on a note, see where that notes takes me. I crash and burn harmonically at times, but in the end, there are always some unexpected shards of beauty in there. Well, beauty to my ears at least, you might think it sounds like I'm completely out of it. ;)
Over and out until next time guys!