"MOZARTROCK": Julia Hamari, mezzo-soprano; Peter Sipos Group. Denon 32CO-1333 (compact disc). First "Amadeus," now this. Those who love Mozart most seem the most determined to do him in. As sick jokes go, this production has no recent contenders. Eleven operatic selections are successively crushed by a heavy, insistent rock beat and Hamari's gulping mezzo. You say her voice can't negotiate the coloratura of the Queen of the Night's second aria? No problem. Sipos' motley crew takes over. You recall that "La ci darem" was originally a soprano-baritone duet? That's easy. Overdubbing gives us two Hamaris for the price of one. None of this failed crossover venture is either remotely clever or illuminating. The performances, one presumes, are definitive. So is the aftertaste.