The Metropolitan Opera's production of Mozart's "The Magic Flute" at the Kennedy Center Opera House on Saturday afternoon might have been a fiasco but for the efforts of two men: conductor Julius Rudel and designer Marc Chagall.

Rudel gave the performance Mozartian musical credibility in considerable measure and Chagall, with his sets and costumes, gave it excitement.

Otherwise, the singing was uniformly without distinction. Even so splendid a Mozartian as Donald Gramm sang Papageno as if he were in a sour mood. But at least his singing was not bad, though it was rushed most of the time. David Kuebler as Tamino and Gail Robinson as Pamina were less satisfying. Their sounds were pinched, their phrasings were prosaic, and Robinson committed the faux pas of the day when she missed her cue in the second act. Sorastro declaimed, "Enter Pamina," looking to stage right. Then there was a pause of more than a minute. Someone in the audience uttered, "What's up, Doc?" And Robinson tardily arrived from stage left. If that was her low point, the relative highs didn't displace it.

Gramm performed an inexplicably unsmiling Papageno, that most ebullient of operatic roles. If nothing else, the Queen of the Night's bird watcher should be funny, but Gramm wasn't.

The Queen of the Night is one of the toughest roles in opera. And Rita Shane's problems in it were no worse than most others'. The Queen must sing coloratura runs with the vocal solidity of a Ponselle and cavatina passages with the gravity of a Schwarzkopf. Mozart was unfair.

John Macurdy lacked the heft for Sorastro and Michael Best sounded feeble as Monosatatos.

Despite all that, it was clear from the overture that something special was coming in this extraordinarily tricky opera. It wasn't perfect. But Rudel, who had almost no rehearsal, achieved a balance among a singing line, evenness of pulse and a richness in the winds that is essential to the work. It is also something that most conductors, for all their trouble, almost never attain. Rudel has shown time and again that he has mastered the Mozart style, with ease. Sometimes he and the singers were out of phase, but this never conflicted with his fluency. If the singers had been able to match him, the performance would have been a model.

The Chagall designs, the other saving grace, were a delight. They lacked the specificity of Maurice Sendak's designs for the Washington Opera's "Magic Flute" last fall. By contrast with Sendak's mordant designs, the Chagall sets tended all to look alike, but the wild splashes of color on each had an outrageousness that seemed right for so bold an opera. And the costumes for the animals--when Tamino starts tooting for them with his flute--were so inspired that the Met should give them to the Metropolitan Museum when this production is retired. That event probably isn't too far off, but heaven help the designer who has to follow in its wake. Visually, this a one-of-a-kind show.