Avant-garde filmmaker, ethnomusicologist, and full-time eccentric Harry Smith was an obsessive record collector who scoured the country for 78s documenting obscure folk artists from the '20s and '30s. Smith would later compile a small fraction of his collection onto Anthology Of American Folk Music, released in 1952 as a six-LP set of dubious legality. Regardless, his efforts proved almost incomprehensibly influential. The artists Smith loved found fans in a new generation of musicians, including future folk pioneers as diverse as Bob Dylan and John Fahey, all of whom shared Smith's obsession with the forgotten figures of American folk. Performers such as Dock Boggs, Blind Willie Johnson, Mississippi John Hurt, The Carter Family, and Blind Lemon Jefferson were just a few of Smith's fascinating finds, and if there's any doubt as to their import, you need only revisit Smithsonian Folkways' astounding 1997 reissue of the entire set with tons of annotation and extras, an event that inspired even more acclaim than Smith's original release. Of course, that was only a glimpse into his massive collection, so John Fahey's Revenant label has compiled another two-disc set of songs Smith had selected for an eventual fourth volume. With a beautiful and informative 96-page booklet featuring essays by Ed Sanders, John Cohen, Dick Spottswood, Greil Marcus, and Fahey, Volume Four (Smith had originally promised six) is stylistically akin to the first three, with some of the artists from the earlier volumes making encore performances. As Spottswood notes, the two-disc set ignores several country developments, as well as the conspicuous invention of the electric guitar in the '30s. Fans can only hope that such key points of musical evolution will be displayed in future volumes, but as it stands, the 28 mostly Depression-era songs on Volume Four run the gamut from labor anthems to fiddle bands to ballads to blues to black gospel. It's another essential, timeless piece of the Americana puzzle, fitting nicely into the incomparable picture Smith painted.