"HARMONY, RHYTHM AND SONG . . . FOR BILL," Public School 81, 256th Street and Riverdale Avenue, Riverdale, the Bronx. A performance by parents who are professional performers in memory of William E. McGinn, a neighbor and firefighter who was killed in the Sept. 11 terrorist attacks. Tomorrow night [2/2/2002] at 7. Tickets: $10; proceeds will benefit cultural programs at the school. Information: (718) 601-5897