Oakland-based blues harpist Mark Hummel can get down and dirty with the funkiest of them, but his real forte is the breezy, jazz-influenced west-coast style, which was sparked by T-Bone Walker's postwar innovations and whose most crucial figure on harp was George "Harmonica" Smith. Hummel's annual harmonica showcase, which he launched in the Bay Area in 1991, is on the road this summer; the lineup changes from city to city, and here Hummel will be joined by Lee Oskar and Billy Boy Arnold. Oskar, best known for his stint in the 70s funk-rock band War, deftly fuses greasiness and pop ebullience, and his version of War's "Low Rider" remains a highlight of his performances. Arnold, born in Chicago in 1935, was featured on some of Bo Diddley's most important sides for Chess Records in the 50s--making him a vital yet unheralded figure in the transition from blues to rock 'n' roll. Lydia Warren opens. Sat 8/26, 9:30 PM, Buddy Guy's Legends, 754 S. Wabash, 312-427-0333, $15.