One of the things that make this score so enjoyable for me is the wonderful guitar playing from the legendary session musician Tommy Tedesco (1930-1997), who played on several John Williams scores including Jaws, The Eiger Sanction, Earthquake and others.
I do not know if this very funny 1996 seminar with Tommy has ever been posted here, but I thoroughly recommend it. He suffered a stroke in the early 90s but even from the little snippets he plays you can recognise that unmistakable playing style. He relates anecdotes about several film composers including Lalo Schifrin, Jerry Goldsmith, Dimitri Tiomkin and Leith Stevens. He also discusses his contribution to The River and cites an unnamed John Williams piece as the hardest thing he had ever been given to play!
The whole thing is great but if you are only interested in John Williams, skip to about 43 minutes in.