Yeah Eddie - you're exactly the kind of guy I hated (e.g. not personally of course - I mean I was very disappointed I lacked that ability) ; )

I have a close friend like yourself - he can jam with anybody, and immediately put his fingers over the right chords. Again, I always wished I could do so. For me a deeper focus on the numbering system / chord function with numbers at least narrows down enormously the next chord that is likely. Many years ago - I would hear the melody not just fine, and then try by trial and error to find the right chord - and that just wouldn't work for me much of the time.

Thanks for sharing your experience in that area. But surely, there are no "aha's" - whether that be music theory, musicianship, showmanship, that you've only been cultivating recently ?