When CHRP founder Lane Alexander got a grant from the Chicago Dancemakers Forum a few months ago, he formed a company--BAM!--and set out to learn "new rhythms" from other tappers. He had no specific agenda, he says; he just wanted to shake things up. And during CHRP's concerts honoring National Tap Dance Day, his new troupe of six debuts a piece with an unusual goal for a tap dance: to show the psychological process of individuation. The dance is set to three of Chick Corea's "Children's Songs," charming piano solos that become progressively more complex, as does the choreography--the ensemble seems to represent the maturing human being. During one rehearsal Alexander focused on the sort of psychological nuance not generally associated with tap, asking his performers to be "more internal," to "pull it in, not show it off." Also appearing on these varied programs are dance legend Fayard Nicholas and his wife (Saturday only) and Tap & Tray, two German tappers who perform in the style of the 30s and 40s; in their showstopping number they twirl waiters' trays, a trick they learned studying with Chicago native Carnell Lyons. Chicago groups Rhythm ISS..., Especially Tap Chicago, and the Chicago Tap Theatre all perform new works, and several other local troupes and individuals offer repertory pieces: Reggio "the Hoofer" McLaughlin and Ernest "Brownie" Brown, Jimmy Payne Jr. and Sarah Payne, Jump Rhythm Jazz Project, Syncopated Seniors, Footprints Tap Ensemble, Perfect Timing, the Timesteppers, Soul 2 Sole Youth Ensemble, and the Center for Dance Tap Ensemble. Vittum Theater, 1012 N. Noble, 773-281-1825. Through May 16: Friday-Saturday, 8 PM; Sunday, 7 PM. $22-$25.