By WENDY COLE

At any given time, a STEPHEN SONDHEIM production is surely running somewhere in the world. Last week in Manhattan's Carnegie Hall the introverted resident genius of musical theater (Sweeney Todd, A Little Night Music) stole the show -- just by turning up. It was an evening of pop, jazz, opera and cabaret, but it was all Sondheim as interpreted by the likes of Liza Minnelli, Glenn Close and Patti LuPone. Sorry you missed it? The lovefest will air on PBS next March, right when the album comes out.