Tuesday's MEDICINE BALL CARAVAN on KRVS (11am-noon Central Standard on 88.7FM locally or at krvs.org) turns your radio blue with the tracks by Pokey Lafarge, Jelly Roll Morton, Mississippi Jook Band, Sister Rosetta Tharpe, Hank Williams, The Velvet Underground, Joseph Spence, Robert Johnson and John Martyn. Also: new in-concert recordings by Sonny Landreth and Tedeschi Trucks Band.