GROESBECK — Cowboy's fiddle, like most fiddles, is ordinary. It is moody, delicate and worn — a scarred spruce and maple body married to a frayed horsehair bow. Often imperfect. Sometimes beautiful.

A good fiddle part elevates a song: It can take a ballad from mediocre to weepy and a bluegrass jig from ho-hum to barn-burning. It's one of the most prominent instruments in country music, and it's a ...