Think all blues sounds the same? Then try the Tenth Annual D.C. Blues Festival. Acoustic guitarist Larry Johnson’s Piedmont blues are made sui generis by his addition of rhythms adapted from the stride piano playing of Fats Waller. Little Sonny Warner is still at it emoting Ray Charles-influenced melodies like he did in the ’50s with Big Jay McNeely. In an ideal world, young Shemekia Copeland’s hurricane strength wail would be heard alongside Lauryn Hill’s, not just on public radio. The Legendary Orioles are a streetcorner vocal harmony supergroup, tastefully backed by the Young Bucks. Headliner Lil’ Ed and the Blues Imperials, with Ed on electric slide guitar, slash through the Chicago boogie songbook. The D.C. Blues Society Band opens. From noon-8 p.m. at Carter Barron Amphitheater, 4850 Colorado Ave. NW. Free. (202) 828-3028. (SK)