“Tap is a family affair,” says Lane Alexander, founder and artistic director of the Chicago Human Rhythm Project, now in its tenth year. He ought to know: using that principle he’s grown this tap-dance festival from a little affair with two days of classes and one performance to a major production with two weeks of classes at Northwestern University and six performances. It’s a matter of inviting the extended family and seeing who shows up. That’s how he got Bill Irwin to emcee for the opening weekend (“I asked him and he said yes”). Same for Savion Glover, the aging wunderkind of tap–now 26, he made his Broadway debut at 12–who’s performed in previous festivals and will appear this year on the opening program. Alexander has even taken the ball and run with it in other cities: within the last five years he’s established Human Rhythm Projects in Minneapolis, San Antonio, Heidelberg, Amsterdam, and Paris, run in conjunction with local organizers. His goal is to establish such projects in 20 or 30 cities around the world, cross-pollinating the world of tap, a form that grows when dancers can see and build on the work of others. A playful attitude is essential, and that’s also embodied in this eclectic festival. August 11: Bill Irwin, Savion Glover, Dianne “Lady Di” Walker, Tedd Levy, Richard Weinberg, Van “the Man” Porter, Lane Alexander, Rhythm ISS, and the North Carolina Youth Tap Ensemble. August 12: Irwin, Jump Rhythm Jazz Project, Shawn Glidden, Brenda Bufalino, Porter, Alexander, and the North Carolina Youth Tap Ensemble. August 13: Irwin, Rhythm ISS, Alexander, Walker, Glidden, Weinberg, and the North Carolina Youth Tap Ensemble. August 18: Lynn Dally, Robert Reed and Six Feet of Rhythm, Rhythm ISS, Alexander, Keith Terry, and Ira Bernstein. August 19: Especially Tap Chicago, Terry, Sabine Koch, Sam Weber, Walker, Bernstein, LaVaughn Robinson, and Germaine Ingram. August 20: Natyakalalayam Dance Company (classical Indian dance), Bernstein, Weber, Walker, Alexander, and Rhythm ISS. Fridays and Saturdays at 8 and Sundays at 3 through August 20 at the Athenaeum Theatre, 2936 N. Southport, Chicago; $15-$25, $25-$125 for the opening-night benefit, which includes a champagne reception and silent auction. Call 312-902-1500 for tickets, 773-935-6860 for tickets and information, 773-296-0869, ext. 15, for group sales and benefit tickets. –Laura Molzahn