At 'b', crosspicked guitar, mandolin fills and chordal banjo. Sty with light simple drums added. Tennessee Waltz Streaming audio sample. At 'b', add 2nd guitar. With mandolin, guitar, acoustic bass and fiddle.
Fiddle plays staccato chops at 'a', fills at 'b'.
Sty with drums added. Butterfat, Dawgfunk Streaming audio sample. The mandolin is slightly less busy at 'b'. At 'b', a '2 against 3' feel and acoustic piano joins in. Nylon guitar, bass and percussion.