Movies from the “good old days” were great because they had spectacular moments within the movie which were not scripted. This happens to be one of those moments, this scene was not in the original script but the directors kept it in because of how good it was. In the scene, a banjo player goes head to head with a guitar player and boy are they good.
Unforgettable ‘Banjo vs Guitar Duel’ From Deliverance (1972) – Golden Classic
Deliverance - Banjo Duel