ON TAP

Iolanthe--Gilbert and Sullivan's confusion-fraught comedy at the Agassiz Theatre. 8 p.m. Saturday and Sunday. Call 496-HRGS for tickets.

A Little Night Music--Spend a weekend in the country with Sondheim's band of mismatched lovers. Loeb Mainstage, 2 and 8 p.m. Saturday, 8 p.m. Sunday. $58 for students.

The Fromm Contemporary Music Series presents a concert of the London Sinfonietta Voices, with works of Montiverdi and Luciano Berio. Sanders Theatre 8 p.m. Saturday. Free.