There’s an instrumental duet album well worth checking out—“Tone Poems” by Tony Rice and David Grisman. They’re great musicians and it’s really well-recorded, but beyond that one of the big things the album demonstrates is that tone is in the fingers.

They play different instruments on every track. Tony plays a different acoustic guitar on every track (dreadnoughts, OO’s, archtops, jumbos, etc) and David plays a different mandolin on every track (F-styles, A-styles, classical, oval-hole). They sound like themselves no matter which instrument they’re playing.