WHEN BILLY JOE McAllister jumped off the Tallahatchie bridge, he hit the movies. And the ripples are still spreading.

It all began in 1967, when Bobbie Gentry's "Ode to Billy Joe" was a big splash on the pop charts. Nine years later, Warner Bros. had turned it into a big hit at the box-office, and in the process pioneered a new idea - using pop songs not simply as the musical score for movies, but as the story-line itself.

That success inspired one of the fastest-growing trends in the business, and produced films from such disparate ditties as "Harper Valley PTA" and "Torn Between Two Lovers." Expected in the near future are versions of "The Gambler," "You Don't Bring Me Flowers" and "Desperado." In fact, so many popular songs are now being turned into movies that the Grammy Awards may have to add a new category: Best Picture.

When the movie industry courting an audience that spent $538 million to see "Saturday Night Fever" and "Grease" and bought 49 million copies of the soundtrack albums, songwriters are the new storytellers. The Eagles, Willie Nelson, Rod Stewart, Elton John, Paul Simon and Stevie Nicks (of Fleetwood Mac) are among the more prominent singer-songwriters whose works currently are being adapted for the screen.

"They're paying gold trying to find songs [for movies]. There's definitely a marriage going down," said manager John Hartman, whose clients - David Crosby, Graham Nash, Poco, Michael Murphy and America - all are developing movie projects from their songs, he said.

"Everyone's bored with just making more money in the music business, so it's "Let's make a movie," " explained Irving Azoff, who manages the careers of The Eagles, Boz Scaggs, Steely Dan, Jimmy Buffett and Dan Fogelberg. Only Fogelberg isn't involved in a song-to-movie project at the moment. "The attitude is basically, "I can't go on the road 'til I'm 80, but maybe I can produce movies 'til I'm 60." " Azoff said.

Azoff, 31, will co-produce "Desperado," a planned Warner Bros. picture based on The Eagles album of the same name. Recorded in 1973, "Desperado" is a concept album of original songs that tell the story of the legendary Dalton gang. The album sold more than 3 million copies, according to Azoff, and the title sone was recorded by Linda Ronstadt.

"What does a hit book sell, a million copies?" asked Casablanca Records and Filmworks president Neil Bogart. "Movie studios go out and pay fortunes for the right to best-sellers. Now they're learning that we have best-sellers, too. Only we sell five and 10 times as many."

In fact, "songs are selling like books," according to Larry Marks, vice president of production at Warner Bros. Studio, which is also developing other kinds of movie projects with Paul Simon, David Crosby, Jackson Browne, Rod Stewart and Elton John. In each case the artist will contribute his own music to a soundtrack album.

"Free Advertising"

With their strong record company and music publishing tie-ins, Warner Bros. and Universal Studios (MCA Records) were a natural to convert "Ode to Billy Joe" into a film.

"Everybody made money on "Billie Joe," and it showed a lot of people that it was quite possible to develop a workable film from nothing more than a song with a good story," said Marks.The story of Billie Joe McAllister is what sold him on the idea of making a movie from the song, said producer Max Baer, who bought the screen rights from Gentry for a flat fee against a percentage of the movie's gross. "There's a mystery as to why the boy jumped, a secret to be revealed," Bear explained. "People are curious animals. They want to find out why."

Screenwriter Herman Rauscher ("Summer of '42") came up with the reason for the suicide, a homosexual experience. Baer made the movie (starring Robbie Benson) for $2.5 million and Warner Bros. distributed it, so far grossing nearly $30 million at the box office, Baer said.

"During the 9 1/2 years before we made the movie, "Ode to Billie Joe" sold 3 to 4 million copies, was covered [recorded] by 100 artists, including Streisand, and was exposed to millions and millions of people. That's free advertising of your product," Baer said.

Still, he maintains that "just because somebody wrote a song that sold a lot of singles and albums doesn't mean it would make a good movie. One has nothing to do with the other."

After seeing the success of "Billie Joe," Phli Borack, a Cincinnati movie exhibitor and distributor (representing 200 theaters), began pouring over the past 15 years of Billboard's Top 100 charts. "I was trying to approach it scientifically," Borack said. "I was looking for songs that told a story, primarily Americana, and obviously something with an enormous identity. "Harper Valley PTA" jumped out at me."

Borack bought the rights of the Tom T. Hall song made famous by Jeannie C. Riley, then independently financed the script and produced and distributed the movie himself, with Barbara Eden starring as the mini-skirted mom who socked it to those "Harper Valley hypocrites." Borack's production company, April Fools Films, invested around $4 million, nearly half of which went for advertising, he said.

"I learned later that "Harper Valley" had a 98 percent recognition factor. It was 10 years old and 98 percent of the people in the country knew that some. That's phenomenal!

"So I knew that even if I made a terrible movie, we'd do a certain amount of business. As it turned out, we did very well." The movie grossed around $20 million last year and it will be re-released this year, Borack said.

In a few cases, studios have agreed to finance a script based on the fact that there were a couple of guys waiting in the outer office with the film rights to a hit song.

"All they had to do was come in and play the song, which we were already familiar with, and it was very, very easy to enter into the deal," said Bill Hornaday, vice president of creative affairs at Avco Embassy Pictures, which recently entered into a deal with producers Ronald Saland and Elliot Geisinger ("The Amityville Horror") to develop "The Night the Lights Went Out in Georgia," based on the Vicki Lawrence hit.

Avco Embassy got more for their money than a title, Hornaday insisted. "Besides the identification with the song, we actually have the [rights to the] song itself so that it can be played at the time of the movie's release," he explained. "We've got the basic synopsis of the movie in the song, which is more than Peter Benchley had when he sat down to start writing "Jaws.""

"Studios love to have a recognizable title, whether it's from a book or a song," said Hornaday. "Right now, acquiring the rights to a song is less expensive than acquiring the rights to a book. A novel has more story, but with a song you have the outline of the story. The depth, the characterizations are determined by the singer, the tone of the music, whether it's upbeat or bittersweet."

The Country Side

"The country and western songs usually have more story to them than rock or pop songs," Hornaday said, adding, "I have a feeling that with this trend people are going to by trying to jack up the prices."

Country singer-songwriter Willie Nelson rode into Hollywood recently with a passel of stories for sale. He's a mini-mogul now, with an office, a secretary and his own production company at Universal Studios, where the screen rights to his 1975 million-selling concept album "Red Headed Stranger" fetched a precedent-setting price, according to Nelson's agent, Jim Wyatt.

Without a script, "Universal paid an amount comparable to what they would pay for a book," Wyatt said. "You could assume it was between $150,000 and $400,000."

Wyatt said that the screen version of "Red Headed Stranger" will remain true to the story and characterizations on the album: a preacher who kills his wife and her lover ("Don't cross him, don't boss him"), then hightails it to Denver with a sheriff in pursuit. Along the way, the stranger shoots another woman who crosses him. The now completed script has been submitted to Robert Redford to play the title role. Nelson and Redford reportedly became friends during the recent filming of "The Electric Horseman," in which Nelson made his acting debut.

Nelson's second project with Universal, his first under a two-year producing contract, will be "The Willie Nelson Story," based on a book currently being written by Pete Axthelm (to be published by Viking Press), Wyatt said. "Universal bought the rights to the book and they'll find someone to adapt it to a screenplay." There will also be a soundtrack album from Columbia Records.

Nelson's next Universal project will be a movie based on his 1974 concept album "Phases and Stages," which tells of the dissolution of a marriage: side one from the woman's viewpoint; side two from the man's.

Meanwhile, back at Warner Bros., Nelson is set to star in "A Song for You," titled after the Leon Russell song that was a hit for both Russell and Elton John early in their careers. The movie will be produced by director-producer Sidney Pollark's production company, said Chris O'Connell, a Pollack associate who will produce "Phases and Stages."

The movie "A Song for You" will be about "a country and western singer much like Willie Nelson," she said. Nelson and Russell just released a duet double album called "One for the Road."

Country and western artists like Nelson, his "outlaw" colleague Waylon Jennings and the more law-abiding Kenny Rogers have become the standard-bearers of what Ken Kragen, Rogers' manager-producer, calls "a tremendous resurgence of country music and country values."

Kragen is producing a CBS-TV movie based on Kenny Rogers' Grammy-winning hit single and album, "The Gambler." Written by Nashville-based songwriter Don Schlitz, "The Gambler" also was recorded by Nelson and Johnny Cash, but Rogers got it into the marketplace first, Kragen said.

To sell the project to CBS, Kragen "simply walked in one day with a huge blow-up of the album cover, a poster, and unveiled it to a couple of network executives. They both said, "Sold.""

"The Place to Go"

The title "You Don't Bring Me Flowers" may make one of the more usual progressions from song to screen. Written by Marilyn and Alan Bergman, the song was recorded last year by both Barbra Streisand and Neil Diamond. After a Louisville radio station executive draw tremendous listener response by electrically combining the two versions into a duet, Columbia Records picked up on the idea and subsequently released the duet as a single. It became a No. 1 pop hit.

The radio executive who started it all, Gary P. Guthrie of WAXY-AM, has filed a $5 million lawsuit against Columbia Records, claiming the company reneged on its promise to pay him for his idea.

Meanwhile, the Jon Peters Organization, the movie production company headed by Streisand's companion-producer Jon Peters, reportedly has optioned the screen tights to the song. Though neither the film company nor the songwriters will discuss the subject, rumor has it that Streisand and Diamong may star.

The fact that "You Don't Bring Me Flowers" has little or no story to it actually is a plus, said "Harper Valley" producer Borack. "You can write any story in the world for that song," he said. "They've got a hit there. If Jon Peters is interested in a co-production deal, all he has to do is call me."

"I believe the commercialization of Hollywood will defeat what we're trying to to in the end," sand David Krebs. "They'll make 50 movies like this and they'll all go down the drain. Still, until they run it into the ground, it's the place to go."

"If you can write a really substantial album that tells a story, there's no reason not to plan in the beginning to pitch it that way," said agent Jim Wyatt. "In the future, studios may want to get involved with songs that haven't been released yet. It makes sense, then they can coordinate the release of the record and the CAPTION: Illustration, no caption; By John Pack for The Washington Post