Maurice Sendak loves queens and kings and quests, magical conveyances, fine Victorian crosshatching and dark and scary caves. He does not fear the silly. He loves wild things, with horns, who roar their terrible roars and gnash their terrible teeth and roll their terrible eyes, but are really rather nice. He loves secrets and seriousness, menace mixed with sweetness, and the courage of the young.

Mozart loved these, too. And Maurice Sendak loves Mozart most of all.

Sendak, who's bewitched people of all ages with such picture books as "Where the Wild Things Are" and "In the Night Kitchen," often draws to Mozart. Of late he's drawn for Mozart. For the production of "The Magic Flute" now being performed by the Washington Opera at the Kennedy Center, it was Sendak who dreamed up the costumes and the sets.

"I'm an opera freak," says Sendak.

He first saw an opera 40 years ago, and tells the story with that same mix of humor, dread and reassurance, that swirls through all his books. "My sister, Natalie, took me to see 'Carmen,' outside, at Lewisohn Stadium, when I was about 12. I still remember how I gripped my chair. From the first note of the overture I was totally transfixed. Then it started raining. It rained and rained and rained until my sister, getting wet, said, 'Come on, let's go.' But I couldn't bear to leave. When Carmen came out on the stage and said, 'Sorry folks, that's it,' I howled with disappointment."

Sendak, 53, a bachelor from Brooklyn who now lives in Connecticut with three dogs and a hi-fi, is a connoisseur of memories. He remembers all the bedrooms he slept in as a child, and the large-sleeved shirts his tailor father made for Shakespearian actors. He still remembers his first glimpses of Schrafft's and Radio City and other wonders of Manhattan, "that Oz across the river." With Proustian precision, Sendak recalls the smells of bread and coffee that came in, with the sunlight, through the window of the subway train as, rising toward the river, it rumbled from the ground.

Memories he cherishes, both bitter ones and sweet ones, are sprinkled through his books.

On a trip to England, at the age of 39, Sendak had a serious heart attack. When he awoke at last, he heard a nurse say "champion," and that word, on a pennant, waves above the city, the city made of bottles, jars and bags and nutcrackers, in Sendak's "In the Night Kitchen." The subway train is there as well. It is pulling into "Jennie Street," a station named by Sendak for his late, beloved terrier. "My mother, for some reason, could not bear the smell of paint," he said. "So every three years, rather than repaint the walls, we would change apartments. She liked to move. I hated it. You see where it says '1717 W. 6th St., Brooklyn, N.Y.?' That's the address of the apartment where I was most happy."

In "Outside Over There," Sendak's latest picture book, Mozart appears, too. Ida, the young heroine, who is "following the stream that curled like a path along the broad meadow," somehow does not notice, just across the water, Mozart in the garden house playing his clavier. Ida, with her magic horn, floats through that strange book like some vision of the Virgin. "Ida will grow up to be a beautiful woman," says Sendak. "She is modeled on Pamina, the heroine of 'The Magic Flute.' "

Ida, chasing goblins, visits Outside Over There, a place of seas and sailing ships and cloudy baroque skies. "The Magic Flute" also takes place in a land that is far off, exotic and yet dreamily familiar. With its greenness and its grayness, it looks as if it might be found somewhere in the thinness of a dollar bill.

Its enlightened heroes, particularly Sarastro, and his Freemason fellows, and the guardians of his temple, look much like George Washington. Dressed in knee-britches and powdered wigs, they gather on the stage like so many founding fathers. But the opera takes place somewhere in antique Egypt, and Sendak's sets are filled with obelisks and sphinxes, monuments half-built, and giant visages of stone half-sunk in desert sands. Sarastro's subterranean temple, where his Masons stride about in chorus doing strange Masonic things, looks as if it's buried underneath the pyramid, the one topped with a glowing eye, on the back of the bill.

Sendak, unlike Mozart, strikes all those who meet him as a thoroughly grown-up, serious, thoughtful man. His body is compact, he wears a rabbi's beard, often as he talks his eyes go dark with sadness. His speech is full of scholarship, he talks of 18th- century Vienna, German romanticism, Victorian books, Haydn and Frank Baum. Now and then he winces. He has gripped the brush and pen so long -- he has done some 60 books -- that he has developed a severe case of bursitis. His talk is dense with knowledge, humor, pain.

Mozart's wasn't. "Like his friend Haydn," writes scholar Frank Kermode, Mozart "showed in conversation, 'absolutely no sign of unusual power of intellect, and almost no trace of culture.' This, the testimony of an admirer, is supported by Ludwig Tieck's memory of the composer as 'small, rapid of movement and with a stupid expression.' "

With its genii and its evil queen, its Masonic mumbo-jumbo, its magic bells and magic flutes, "The Magic Flute," if truth be told, has a plot that's sort of dumb.

Sendak will hear none of that. "People think 'The Magic Flute' is the kind of opera they ought to schlep their children to -- and they're not wrong. But what I love most about it is its seriousness of purpose. It is about enlightenment. People laugh at the Masonic stuff, but Mozart didn't. He was a Catholic who became a Mason, who felt grounded in Freemasonry. He was a prodigy at 6. By the time he wrote 'The Magic Flute,' he was writing for himself. He treats his heroine, Pamina, with remarkable compassion. Everyone tells her her mother, the Queen of the Night, is a psychopath. How would you like that? Pamina is so depressed, so totally bewildered, that she contemplates suicide -- until those three genii, those three little children in an amazing trio convince her she should choose to live. For someone interested in children, as I am, that's a glorious business."

Most of Sendak's books, like the four operas that he's designed, have been collaborations. Sendak, who made these sets for Houston, worked them out with Frank Corsaro, the director of the opera, and with Neal Jampolis, who "realized" their many flats and scrims and drops.

Inevitably, perhaps, all those colonnades and caverns, ruins, half-built monuments and rocks that suggest faces, compared to those in Sendak's books, do not quite come off. Sendak, in his pages, places his young heroes in tiny, cozy spaces, but you can't do that on the stage. Sendak, in his books, rounds his goblins (who are babies), his monsters (who are pals), and his bottles (which are buildings) into full believability. But on the stage, the singers stride through blown-up drawings; his sets, despite their crosshatchings, seem a little flat.

They are playfully profuse with all sorts of arcane Masonic paraphernalia -- with set squares, floating eyes, and pyramids that glow. They are also filled with many bits of friendly nonsense, with great stone beasts that stick their tongues out at the audience, with flames that eat the queen ("like all stepmothers and witches, she is, at last, kaput"), and with a large hot-air balloon, which, whenever needed, descends from the sky, delivering, for instance, Pamina's three young saviors. They wear gold Pharaoh skirts, no shirts and white 18th-century wigs.

Children, and grown-ups, too, do not doubt the truths of Sendak's perfectly paced books. Submitting to his "Magic Flute" demands another level of suspended disbelief. "I know," says Maurice Sendak. "That's opera. You have so much to step over. But it is worth the trip."