IMHO the place to start would be "Robert Johnson: The Complete Recordings" on Columbia/Legacy. The blues just about started here, and it does not get much deeper or more profound. The 2 CD set contains all the material Mr. Johnson ever recorded. The recordings are from 1936-37 and were first released on 78rpm, so no audiophile stuff here in terms of room, perspective, details....but anyone who loves the blues should own this. Sorry, but I can't think of any really GREAT all instrumental (traditional) blues albums. Enjoy the music! Robert.