Chauvinistic English critics are calling Thomas Ades, 28, the hottest composer since Benjamin Britten. Don't believe the hype. Ades' first opera, just released on CD, is a thoroughly nasty piece of goods. Philip Hensher's sneering libretto tells the scabrous story of the decline and fall of Margaret, Duchess of Argyll (the "Mrs. Sweeny" of Cole Porter's You're the Top), who liked to do the Full Monica on her male servants. Ades' score is a glib farrago of sour, splintered vocal writing, postmodern pastiche and cartoony sound effects. Is this the music of the future? No, just further proof that the now exhausted classical-music avant-garde is repeating itself--this time as camp.