Roy Harris's "Folk Song Symphony" is a choral work - did he do any purely instrumental ones?

One of my favourites is Bartok's Second Rhapsody for violin and orchestra, where he takes the tune known in America as "Simple Gifts" and takes it to much more interesting places than Copland did (and about 20 years earlier). I presume it's an Eastern European tune originally.

Prokofiev's Second String Quartet is a terrific piece based on Circassian folk tunes:
http://www.CircassianWorld.com/Prokofiev_StringQuartet.html