Most opera houses ring in the New Year with Johann Strauss Jr.'s most popular operetta--the festiveness of which is appropriate for the occasion--and this December 31, 1983, Covent Garden performance follows suit. An exceptional cast--led by Hermann Prey and Kiri Te Kanawa as the couple whose marriage survives the comic indiscretions of three long acts--obviously has as much fun as the audience. Plácido Domingo leads the Orchestra of the Royal Opera House through its paces with panache. Prince Orlofsky's Act II party is always a splendid opportunity to pull out all the stops with surprise "guests," and this performance makes the most of its chance: entering the proceedings to sing one of his tailor-made chansons, "She," is French crooner Charles Aznavour, who is followed by dancers Merle Park and Wayne Eagling, their delightful pas de deux flashily choreographed by Sir Frederick Ashton.