It is a warm, sunny Sunday morning in New York but the fans of WNEW-AM deejay Jonathan Schwartz are shut up in their apartments by choice. In the world of radio, dominated as it is by hard and soft rock, phone-ins and all-news, Schwartz is the keeper of a special flame devoted to the likes of Frank Sinatra, Ella Fitzgerald, Mel Tormé, Rosemary Clooney and Tony Bennett. Where else on the dial can you hear Danny Kaye's narration of Tubby the Tuba juxtaposed with Bessie Smith, Crosby, Stills & Nash, Woody Allen and Louis Armstrong—with a recipe for leg of lamb for good measure?

It is possible that Schwartz, 48, knows more about America's pop standards than anyone on the air. Ed Bradley of 60 Minutes says, "Jonathan is unlike anyone else I've heard on the radio. He seems to know everything about everything. But he doesn't just talk at you, he holds a conversation with his listeners." NBC newswoman Linda Ellerbee raves that Schwartz "speaks with and to intelligence. Besides Garrison Keillor, Jonathan is the only person I can listen to constantly. He gets you to see and listen to music in new ways."

Though he's on the air other times, it's Schwartz's five-hour Sunday morning show that really gets his innovative juices flowing. In a whispery, almost seductive voice, he'll read a passage from E.B. White, speak about the art of avocado presentation or call a meteorologist friend in Palm Springs to get the forecast there. Norman Mailer, Jerzy Kosinski and New York Governor Mario Cuomo have all joined him to chat about their favorite recordings (Cuomo stayed for two hours). And, at the slightest excuse, there's baseball. His love affair with the Red Sox verges on the obsessive, and on Super Bowl Sunday, he presents what has become over 15 years a legendary, irreverent salute to the national pastime, featuring songs and bits of old play-by-play broadcasts. While in Paris and Palm Springs, he has arranged to listen to ball games via telephone, an expense, he admits, that "brings new depth to the word exorbitant."

Schwartz was born into Tin Pan Alley. His father was Arthur Schwartz, the composer of such classics as That's Entertainment and Dancing in the Dark, and his mother, Katherine Carrington, was a singer and actress. When Jonathan was young, the family moved from Manhattan to Beverly Hills, where his father produced movies. He can recall Judy Garland singing at the foot of his bed and Jimmy Durante smashing the piano at one of his parents' parties.

Despite the lively showbiz activity, Schwartz, an only child, describes his early years as unhappy. "I was fairly solitary," he says. His mother, who died of hypertension when he was 13, was ill throughout his childhood; retreating into a fantasy world, he discovered radio. "It had a magic for me from the first moment I heard it," Schwartz says. "The use of the imagination in radio listening always struck me as unbeatable." He even made up his own station, WBCY, and "broadcast" out of his closet every morning before school. Carly Simon, a childhood friend, says, "Jon-o turned me on to Ella Fitzgerald and Peggy Lee and a lot of the singers that I emulated."

After dropping out of Columbia, Schwartz got his first radio job as a disc jockey at WBAI in New York in 1958, broadcasting one-hour shows. Four years later he moved to Paris, where he sang and played piano in a nightclub, but returned to New York nine months later for the World Series. In 1968 he was hired at WNEW-FM, a progressive rock station. "The new music was a puzzle to me," he says. "But I liked it. It was a whole new way of expression and feeling and it coincided with the environment into which it was born. But my father [who died in 1984] never understood it and felt great contempt for it." In 1971, Schwartz broadcast his first Sunday show on the station's middle-of-the-road AM branch, where he played the old standards on which he'd been raised.

To some critics, that means more Sinatra than the world needs now. Frank has been Schwartz's favorite singer ever since he heard a 1952 record of Birth of the Blues. "That recording was so potent and dramatic and virile," says Schwartz. "Sinatra became the musical novelist within me." In fact, Schwartz has almost every recorded note Sinatra ever sang plus hundreds of hours of unreleased sessions. For years these underground tapes were an integral and much anticipated part of his show. Then one Sunday in 1980 Schwartz sneak-previewed Sinatra's Trilogy set. Although he praised two of the records, he called the third, Future, "a shocking embarrassment." Two days later Schwartz was off the air. It was reported that Sinatra was so incensed at the criticism that he got Schwartz fired. Jonathan returned three months later, but his version of the incident is still cryptic. "I was not fired," he says. "I was given a sabbatical. As to what happened, you had best ask Sinatra." He still plays Sinatra. "His music is what counts," Jonathan says.

Schwartz has published two books of fiction and also sings at Michael's Pub, a Manhattan nightclub, and recently released Anyone Would Love You, an album featuring his father's music. His own love life has had its share of the blues. In 1968 Schwartz was briefly married to writer Sara Davidson. Seven years ago, he wed free-lance writer Marie Brenner, whom he had met in the press box at Yankee Stadium when she was covering the Red Sox for the Boston Herald American. They have a daughter, Casey, 3½, and he still considers Brenner "one of my closest friends." In 1984 he married stage producer Elinor Renfield, 39, whom he'd been seeing on and off for 16 years.

Schwartz is not universally admired. One writer has called him "a legend in his own mind." Recently Schwartz received a letter asking, "Has it ever occurred to you that you are the most conceited, mannered, condescending person ever to speak into a microphone?" But most people react more like Ed Bradley. "Jonathan has no small ego and he is opinionated," Bradley admits. "I don't agree with everything he says and I don't like everything he plays. But if I'm in New York and it's Sunday, my radio will be on."