Billie Redden plays a mean banjo.
Well - he doesn't play it. A body double does. It was performed for the film by Eric Weissburg and Steve Mandell, and dubbed in for Bille Redden and Ronny Cox.
The composer of "Duellin' Banjos" (a guy named "Smith" I think) successfully sued the filmmakers, as the song was used without his permission.....
EDIT --> Yes - some of that relied on Google. But I remembered most of it.....