When I speak that there are authentic partimento FANATICS I really mean it. I got literally students who did last year left after me mentioning functions. They would then left the most important voices regarding concert improvisation in Germany, Nederland and England then?
But this has a reason to be: function theory is often taught as an academic doctrine of overwhelming mystical signs thrown everywhere over a musical score.
Here you see a shot from the amazing work of Richard Amon at the MDW in Vienna. I am happy to own his main publications since long time ago. This – togheter with my experience as composer and musician student of music theory – allowed me to see what (from my point of view as a composer) is superfluous complexity and complication , keeping only the “juice” for you. https://www.universaledition.com/en/Amon-Lehr-und-Handbuch-zur-Funktionstheorie-und-Funkionsanalyse/P0165721