This week on “The Juke Joint," Robert Barclay previews the Chicago Blues Festival, the world’s largest free blues festival. He includes work by Buddy Guy, Shemekia Copeland, Nora Jean Wallace, Lil’ Jimmy Reed, Corey Harris, Southern Avenue, Kim Wilson, the Cash Box Kings and centennial tributes to Dinah Washington, Otis Spann and Jimmy Rogers. The festival dates are June 6-9 in Millenium Park, Chicago.