Quite a change of pace from the adulterous intensity of Inspector Proby's Christmas (1994): The liaisons among the members of the seat-of-the-pants Floria Tosca Grand Opera Company are just as amorous and irregular, but they're played mostly for laughs, even when they erupt in murder. The company's proprietor and musical director, George Sinclair, has fallen out of love with beefy prima donna Maria Cellini and into the arms of China- doll mantrap Isabelle Morny, who turns out to be his half-sister. Meanwhile, producer/director Jane Nuneham is neglecting her stage-manager husband Edmund for the muscular embraces of the new Don Giovanni, Winston Wheeler, as alcoholic tenor Rupert Brock's silent understudy Tino Tragliava (nÇ Tim Grant) hovers pansexually behind the scenes. So why is the Floria Tosca's not- quite-triumphal tour of Cornwall's stately country houses interrupted by the murder--not of Rose Bolitho, the host's daughter, who's taken a fancy to George--but of irascible corporate sponsor Clay Hammerson, who's not even sleeping with a single member of the troupe? Though the cast is passionate, the tone is genial and urbane, concealing the plot's complications and culprit perhaps a bit too well. Opera buffs won't care, nor should they.