Quoting from the liner notes of "Canned Heat Blues" (RCA/BMG/Bluebird):
"In _Deep Blues_, Robert Palmer's excellent, and essential, book about the history of the blues, (Tommy)Johnson's older brother, LeDell tells scholar David Evans that "the reason he knowed so much (was) he sold hisself to the devil. He said, 'if you want to learn how to play anything..and how to make up songs yourself, you take your guitar and...go where a crossroad is...Be sure to get there a little 'fore twelve o'clock that night..Have your guitar and be sittin' there playing a piece..A big black man will walk up there and take your guitar, and he'll tune it. And then he'll play a piece and give it back to you. That's the way I learned how to play anything I want.'" End quote.

This is one of the standard legends of the blues, probably told by bluesmen to mystify their audiences and impress women. Tommy Johnson, who may have been a cousin of Robert Johnson, actually learned from Charlie Patton and Willie Brown (the same mentioned in Robert Johnson's Crossroads Blues "Run you can run, tell my friend, boy, Willie Brown..."). He is best known for his great song "Canned Heat Blues" which describes the alcoholism that actually ruined his musical career.