"I asked for the Nelson Riddle Orchestra, but they told me it wasn't on the budget," quipped Germaine Ingram -- one third of the Philadelphia Tap Dancers -- during their performance at Baird Auditorium Sunday afternoon. The line got a laugh, but it also made one realize that these fabulous dancers -- master tapper LaVaughn Robinson, Sandra Janoff and Ingram -- were performing virtually a cappella. Except for some clapping and Ingram's occasional singing of a standard tune, the sound came completely from their six expressive feet.

And what sound! The jovial, bearded Robinson, a 50-year veteran of the art form, is a rhythm tapper par excellence, and his younger associates can lay down some mean riffs as well. All three favor a gutsy, unadorned style and there is never a trace of artifice in anything they do or say.

The trio's program, presented in conjunction with the National Museum of American History's "Hollywood: Legend and Reality" exhibit, was loosely structured around dancing celebrities. Robinson offered a piquant impression of Bill (Bojangles) Robinson imitating one-legged hoofer Peg Leg Bates, and a beautifully articulated interpretation of Irish tapper Pat Rooney's style. Ingram paid homage to Fred Astaire with an introspective, elegantly curving solo. The troupe joined forces for a high-flying tribute to the king of the wing step, Bill Bailey, and for a soft-shoe reminiscent of Honi Coles and Cholly Atkins.

After wowing the enthusiastic audience with back-to-back solos of awesome control, timing and imagination, Robinson asked if there were any tappers in the crowd who wished to join him on stage. More than 30 people, ranging from preschoolers to grandmothers, donned their tap shoes and finished off the performance by learning a frisky routine at the feet of the master.