If Orson Welles hadn't asked Nesuhi Ertegun to organize a New Orleans-style jazz band for a radio show in the 1940s, Ertegun might not have gone on to become one of the world's most powerful record executives.

And Ertegun probably wouldn't have put to practical use all the experience he got entertaining and listening to Duke Ellington's band in his home -- the Turkish Embassy -- in pre-World War II Washington.

As the son of the Turkish ambassador, Ertegun had more than the usual opportunities to pursue his love of jazz: He frequented the Howard Theater and often invited the musicians to come by the embassy for dinner and jam sessions. When he moved to California as a student, he took his jazz habit with him and opened a record shop; Welles was a regular patron. At the actor's request, Ertegun put together a band of New Orleans immortals -- Mutt Carey, Jimmy Noone, Kid Ory.

I'll never forget the first day the band rehearsed," recalled Ertegun, now president of WEA (Warner/Elektra/Atlantic) Records International, here to deliver the keynote address to the Radio Free Jazz convention over the weekend.

"Welles came into the studio with his entourage and asked me to introduce him to the musicians. I took him around to everyone.But Ory was hard of hearing. He said, 'What'd you say the name was?' I thought to myself, 'Well, we're out of this job now.'

"But Welles said, 'Mr. Ory, I'm a great admirer of yours, I have all your records and those where you play with Louis Armstrong and the Hot Seven.'"

The mail reaction to the group's first broadcast was so heavy that the band stayed on the network show for 13 programs. But no one offered to record them. So Ertegun did it himself, launching his meteoric career.

His brother, Ahmet, had started Atlantic Records in 1947 and was trying to keep the company afloat. Nesuhi joined Alantic in the 1950s and produced some of the most important jazz records of the period by such artists as Charles Mingus, John Coltrane and the Modern Jazz Quartet. Meanwhile, the company went on to make a fortune by recording pop stars: Ray Charles, Aretha Franklin, the Drifters and Roberta Flack.

In 1967, Atlantic Records was sold to Warner Bros. Seven Arts, Ltd., for $17 million. Ertegun became president of the international division of the resultant conglomerate.

Now he spends eight months a year in Europe, Asia and South America. "I live in airplanes," said the executive. "I could use the telephone, but I believe in personal contact. Other companies, Columbia, RCA, Polygram, EMI, were doing this years ago -- multinational record sales. But we're just getting into it."

Ertegun is probably the only record company executive who's expert on both jazz and soccer. A devotee of the latter since childhood (he's been to every World Cup match since 1966), he is chairman of the New York Cosmos, champions of the North American Soccer League in 1977 and 1978. The club, a component of Warner Communications, Inc., was formed in 1971 at Ertegun's suggestion. WCI executives bought his idea and helped introduce the sport to the U.S. by signing such stars as Pele and Franz Beckenbauer. t

Ertegun, 61, favors Italian-cut suits; his custom-made shirts and ties always match. Although he speaks a half-dozen languages, his English is that of a person who's lived in many parts of the U.S. -- a mishmash of regionalisms.

After four marriages, Ertegun became a father for the first time only five months ago. "I plan to have more children," he said. "I find it an exhilarating experience."

As president of WEA International, Ertegun supervises thousands of employes and 21 foreign companies that come under the multinational umbrella. Ertegun's task is to sell the WEA product overseas and look for foreign artists.

Like American record sales, those in foreign markets have declined recently, but Ertegun forecasts a resurgence. Another industry problem which concerns him more is the illegal sale of records and cassettes not manufactured by licensed companies.

"Piracy is eating away like a cancer," he lamented. "In Italy, 60 percent of the cassette sales are pirated. In some places like Singapore and Indonesia, it's 80 percent. In the United States, it's only 5 percent because of the FBI. Hong Kong is clean. But there's a different problem in West Germany and Japan. People there tape music at home and exchange the tapes."

Jazz is still Ertegun's musical addiction. "I just got a copy of a Thelonius Monk/Pee Wee Russell record that I'd been looking for for several years," he said.

He is equally passionate in his dislike of fusion (jazz-rock) music. "Fusion is an assault upon our ears," he said in his keynote address to a gathering of 354 record company executives, radio programmers, critics and nightclub operators. "I hope that someday the entire audience will get up from one of those concerts and leave."

"It's very difficult for jazz musicians to understand why their records don't sell as much as pop or rhythm 'n' blues. Jazz has never been a majority music. It's too subtle. It has too many contours.

"Harold Robbins outsells Faulkner 100 to one. The Bee Gees outsell Dizzy Gillespie. And no amount of promotion is going to change that.

"But to make the point that jazz is the only American art form is not enough -- it's important as an art form. Duke Ellington is as important as William Faulkner and Louis Armstrong is as important as Ernest Hemingway. wBut the role of jazz in American culture has never been properly understood." b

Ertegun prides himself on having understood that role from the beginning. He started listening to jazz as a teen-ager in London while his father was the Turkish Ambassador to England. Later he studied at the Sorbonne. By 1939, when he came to the U.S. on summer vacation to visit his parents, he and his brother, Ahmet, began amassing a collection which grew to 25,000 records.

The outbreak of war in Europe prevented Ertegun from returning to Paris. He began promoting jazz concerts.

"You can't imagine how segregated Washington was at that time," he said. "Blacks and whites couldn't sit together in most places. So we put on concerts at the National Press Club. Jazz was our weapon for social action. It played a historical role."

All the while, Ertegun frequented the Howard Theater to hear Ellington, Jimmie Lunceford, Andy Kirk and other favorites.

"I used to invite Duke and the band members to my house," he recalled. "They'd come over sometimes for dinner and bring their instruments. Can you imagine Harry Carney, Johnny Hodges and Barney Bigard playing for a student and his friends? It was one of the biggest thrills in my life.

"I remember once there was an embassy party, and I was having some musicians over at the same time. We were really getting kind of loud, and I was worried that maybe the people outside could hear us.

"At about that time my father peeped in and said, 'Can you leave the door open? That music sounds awfully good.'"