From Gil Scott-Heron and Gunther Schuller, not to mention Duke Ellington and George Gershwin, orchestral composition for jazz has been a stream flowing somewhere at the borders of popular music. In Deep River, guitarist-composer Richard Nelson has conceived elaborate arrangements for material found on Harry Smith’s Anthology of American Folk Music, an LP collection of old-time recordings that spurred the folk-blues revival of the 1950s and ’60s. Unlike the raw-boned performances discovered by Smith, Nelson has crafted and polished the pieces, playing with instrumental timbres and imaginatively reconceiving simple tunes into a complex suite.