Think of the Bach motets, with and without instrumental doubling, from which Mozart said he could learn something: What Mozart didn't notice is that they turn the human voice into a completely mechanical instrument (in a way that he, for one--despite what Toscanini said about Don Giovanni--never did) and the effect is ghastly; rather like embalming somebody, and achieving that "desirable, life-like appearance," before he's dead. Or like (as the Japanese sometimes do) hanging artificial, paper cherry blossoms on living cherry trees. Not like the genial imitations, say, of crickets and frogs, using human voices, that Josquin and English and Italian madrigalists sometimes indulge in; which manage both to astonish and to please, and never to lose their intrinsic vocality.