i can still hear those fiddle riffs from Shaft.
I can hear them too. Issac must have met his own “George Martin’ musically speaking. George Martin is the man who arranged most of the classical string work for later Beatles songs, such as “All You Need Is Love” or Day In A Life”.
As far as I have read, Issac never did learn how to literally write music using the common notation.
Obviously, he learned and communicated by ear. Most music teachers back then discouraged this kind of spontaneous learning.