Is Leonard Bernstein's Candide, an adaptation of Voltaire's philosophical satire, an opera or a musical? The controversy has dogged this remarkable hybrid ever since its debut on Broadway in 1956. Certainly Bernstein's background—celebrated conductor of the classical repertoire who crossed over to musical theater with Wonderful Town and West Side Story but failed in his only true operatic effort, Trouble in Tahiti—added to the confusion. His collaborators—Lillian Hellman and Hugh Wheeler penned separate books, and Richard Wilbur, Stephen Sondheim, and John LaTouche contributed the lyrics—were highly regarded theater folks with minimal operatic credentials. And Bernstein's cleverly constructed score—an amalgam of delectable and wickedly witty tunes evocative of Mozart, Offenbach, Gilbert and Sullivan, and Tin Pan Alley that only operatic voices can do justice to—mocks the pretensions of high art. (This irreverence, which is, after all, central to Voltaire's role in the Age of Enlightenment, seems just right for the awestruck hero's adventures.) The public embraced this American classic long before the opera establishment, which waited till 1982 to give its blessing with a New York City Opera production. Lyric Opera is a Johnny-come-lately, but to make amends it's assembled a first-class creative team. The director is Broadway wiz Harold Prince, and the conductor is George Manahan, who wowed Lyric audiences last season with his fluid, dramatically coherent pacing for Susannah. The top-drawer roster of operatically trained singers features baritone Timothy Nolen (as Voltaire and Dr. Pangloss in assorted guises), soprano Elizabeth Futral (Cunegonde, Candide's naive sweetheart), and Phyllis Pancella (as the Old Lady). Opening Saturday, 7:30 PM, and running through Thursday, December 22, at the Civic Opera House, 20 N. Wacker; 332-2244.