The way I think of it is “can you hum the tune?” I am pretty well versed in classical music, and for the life of me I could not hum any of the themes in the LOTR trilogy. And I have just watched the whole set again about a month ago.
Star Wars? Yes.
Indiana Jones? Yes.
Baron Munchausen? (just to include non-Williams) Yes.
The Natural? Yes.
Pirates of the Caribbean? Yes.