It looks like a Broadway musical, sings and dances like one and with a six-figure budget it certainly costs like one. But what the audience in the Hyatt Regency's black-and-glass ballroom is nervously waiting to see is something else again.

For despite the swell budget, this show will be seen just once, and by a very select group: 1,735 Datsun dealers and wives. And its original score and lyrics aren't about hope, heartache or any of that mushy romantic stuff. They're about cars, and the only love that dares speak its name is the love between the consumer and his favorite auto. This is not "Oklahoma," or even "Fiddler on the Roof." This is (drumroll!) "The Datsun Difference."

Welcome to the world of industrials, a billion-dollar-a-year operation that remains one of the least known facets of show business. Snazzy, jazzy, upbeat and uptempo, industrials use some of the best talent in New York and contain enough pep and vim for a dozen Broadway shows. Stars like Carol Burnett, Angela Lansbury and Robert Morse have been in them, but merely beguiling the tired businessman is only half the battle. You have to get that message to Garcia.

They are marvelous to watch, these industrial shows, kind of a Highlights of the Greats White Way, an hour or more of nothing but slick opening numbers peopled exclusively by limber chorines, suave singers and new cars. The magic of a live theatrical experience compells attention, but it is the words, carefully prerecorded and amplified to insure clarity, that provide the key.

It starts with the bouncy "Steppin' Up The Datsun Line" ("He wants the performance of Zee, Zee, Zee, She wants space and luxuree, ee, ee"), letting the dealers know why new cars are in the offing. And who can forget "Show Me," a torchy plea to get salesmen to increase demonstrations: "The rockets start to shoot when I clutch it." And last comes the inspirational "Datsun Pride" finale, where everyone joins in to sing "You made Datsun what it is today, American's seeing the Datsun way." When the lights go on and those dealers and their wives look meaningfully at each other, who can say it hasn't been an instructive, not to say moving experience?

"Demonstrate, demonstrate, demonstrate, that's what Jesus Christ did and that's what we're about. "That is the word from a 90-year-old man with the delightfully improbably name of Jam Handy. a devout Christian Scientist, a two-time Olympic bronze medal winner - the 440 breakstroke in 1904, water polo in 1924 - who somehow found time to think up the whole field of industrials. It can all be summed up, he says, by the ninth verse of the fourteenth chapter of St. Paul's First Letter to the Corinthians.

"So with yourselves: if you in a tongue utter speech that is not intelligible, how will anyone know what is said?For you will be speaking into the air." Ginger Rodgers Loved It

Industrials are seasonal, like migratory birds. Electronics companies. RCA. Sylvania and Zenith put theirs on in the spring. American car firms - like the terribly elegant Cadillac show, where the women all wear floor length gowns - monopolize the late summer, foreign cars, like Datsun, take up the turn of the year, and soft drink companies dare to have two shows, one in the early spring for bottlers, one in the fall for fountain folks.

Industrials come in all sizes from slide shows for 50 people to giant productions like the Millken fabric show which runs for two weeks every year and has a cast of 40 Chevrolet used to have the biggest extravaganzas of them all sending five stock companies to 30 cities at a cost in excess of $5 million.

Industrials, obviously, are big business. Many of the companies running them are named after founders - Jam Handy, Bill Sandy, Herf Kerbawy - and cluster around Detroit, close to the lucrative car industry, to compete for the big contracts. St. Louis based Communico, the producers of the Datsun show, employs more than 200 people and on the basis of 380 clients and a 53-live-show-per-year output, considers itself the largest American producer of what it calls "business meetings."

When Communico got the J.C. Penney contract. One of their executives spent "a solid week" with Penney's chairman of the board, flying with him on his private plane just to be exactly sure he knew what kind of personality the show was to have. Once completed, it was so successful that Ginger Rodgers, seeing it from the audience, thought it was good enough to go to Broadway.

Industrials can also look quite funny to the unitiated, and can seem hopelessly surreal in conception and execution. What is one to make of a musical put on for funeral directors? Or of the International Harvester show, where the tractors are bigger than the actors? Or of a Crane Plumbing Fixtures production called "Put the Blame on Crane?" Or of a home insulation show with the hit song, "You Call It Shingles, I Call it Shangles." Or the time a brand new Ford, scheduled to rise gracefully out of the orchestra pit, rose a bit too fast and was presented to an expectant audience with its roof totally smashed in. Does Money Matter?

Who would want to be in one of these silly industrials, you might wonder, who would want to have to put feal feeling into lines about fully independent suspension and radial tires. The answer is who wouldn't?

"The majority of New York actors are fighting to be in these, hundreds of people come to auditions, my phone doesn't stop ringing," says Datsun director/choreographer Robert Herget, one of the best in the business, an easygoing veteran of numerous legitimate, TV and industrial shows. "It's a good training ground, like vaudeville used to be.They get to spread their wings, and if they fail it won't hurt them."

The three men and four women selected for the Datsun cast ranged in industrial experience from Vicki Belmonte, who had appeared in $54 previous shows and is known as "Queen of the Industrials" to Alan Weeks, who'd just left the title role in the Broadway production of "The Wiz" and had earlier appeared in no more than a couple of these productions.

Actors and actresses in these shows seem to have varying degrees of ambivalence about their work. They view them as larks, as good opportunities to travel, to let the wind blow through their minds. But this is always balanced by the lack of cachet, by the fear that one can be trapped in industrials with no way out. One consideration, however, inevitably takes precedence: money. For industrials pay almost double the Actors Equity minimums for comparable Broadway work.

"People do look down on the creative aspect, they say "You're singing to slides, talking to tires, making love to cars," says Alan Weeks, earlier seen as the man Gene Hackman caught picking his feet in Poughkeepsie in "The French Connection." "There's no great allegiance to the product, no aura of camaraderie like on Broadway. In industrials, everyone comes in, does the gig and splits. But for an entertainer, it keeps you in tune between jobs, it keeps your instrument working. And they pay money.

Money was also a prime lure for David Blomquist, who wrote the Datsun show and earns a six-figure salary largely by writing industrials. A tweedy, pipe-smoking type, he is aware that industrials have been called "nothing but two-hour commercials." He knows that "if Clive Barnes came and saw this he'd say, "Well..." and he knows he is writing for "the TV audience, people who don't eat health bread or read the Village Voice." Yet despite all this, and over and above questions of money, he finds himself "endlessly fascinated" by industrials and what they can do.

"Policemens' lives are dramatized, but the average salesmen or worker never gets a chance to see his business in any way dramatized," Blomquist explains. What happens when they do, he says, can be quite revealing:

"A color TV tube plant where the labor force was one third Puerto Rican, one third Appalachaian white, and one third inner city black, all with an average 9th grade educations level, was having a 40 to 50 per cent rejection rate for its product. They had tried industrial psychologists, efficency, experts, nothing worked."

What did work was "a series of musicals we staged, like little soap operas, based on life in the plant. We ran 15 in the course of a year, and we had a dramatic turnaround in the rejection rate, in fact we had it headed toward zero."

What this means to Blomquist is that "we have to make work more interesting. People have to feel they belong to something, people have to get a feeling of community. I know that's corny, but its true. And industrial shows are a way of reaching people about what they do."

Why do they do it? Why does practically every major corporation in America spend hundreds of thousands of dollars on a strictly in-house show that will never ever be available to the public at large?

The answer goes back to Jam Handy and the Midwest in the early 20th century, to men now deified as pioneers of American business, men who Jam Handy remembers like it was only yesterday.

There was John H. Patterson, for starters, founder of National Cash Register and considered the creator of modern sales practice. He hired Handy off the Chicago Tribune in 1911 to run his NCR Schoolhouse - a theater where prototype sales situations could be acted out for the benefit of new salesmen - because among Handy's 72 jobs at the Tribune had been the editing of the weekly dramatic supplement. "I had contacts with Belasco and Shubert, don't you know, and George Cohan and Ziegfeld, so I talked a very good line of show business," Handy remembers today with a bemused chuckle. "In the country of the blind, the one-eyed man is king, so I was the authority on showmanship."

Industrials really started to boom in 1924, when R.H. Grant a colleague from the NCR days, had become head of sales for Chevrolet and let Jam Handy Organization had been in business for a dozen years.

"There were 11,000 Chevrolet dealers, 16,000 retail salesmen, and we had no way of reaching them all." Handy says. "We decided the only way to get these dealers together, if we were to inform 'em on Chevrolet, was in theaters. And since I had become acquainted was again the light in the darkness."

No one not even Handy had any conception of the enormity of what he had begun. "It just grew," he says, still a bit surprised. "First came those dummy sales demonstrations. We'd sing songs that ridiculed our competition, but at first we didn't have anybody who could sing. So it all evolved gradually, until it came finally to where we'd have casts of 20 and 30 and we wouldn't put anybody on unless they could speak beaytifully."

Industrials have gained greatly in sophistication since the early days of what Michael Murphy, assistant general manager of Communico's business meetings division and the producer of the Datsun extravaganza, calls "dog and pony shows, where someone would hold a card saying sales were up 47 per cent and a girl would come out and sing, "There's no business like the Bendix business." "But despite slick multimedia presentations which in Datsun's case included five slide projectors, a 3-D segment involing an Academy Award winning cinematog rapher and literally tons and tons of equipment, the basic purpose of industrials has remained surprisingly constant.

That goal remains, says Michael Murphy, "to motivate and to inform. A little show business, a little pizzaz, never hurt."

And it works, says Bob Kent, Datson's vice president for marketing services. "These things develop a tremendous esprit. You take a small dealer from Iowa or someplace, this poor guy thinks he's out there all alone. Butthen he finds out there are 900 other people with the same problems, the same concerns that he has. We think that's very good thing." Show Time

The Datsun dealers here in New Orleans don't know from such elegant arguments. Nor do they know from all the trouble the Communico people have had just physically putting together all the equipment for the show, enough equipment to fill one 44-foot truck, two 22-footers and a 18-footer to boot.

The problem was that though "The Datsun Difference" was scheduled to begin at 1 p.m. Thursday, the hotel ballroom wasn't available until 1 a.m. Wednesday, meaning that the 40-odd people involved in the process, which included constructing a 110-foot stage and hoisting a six-ton light grid, have literally been working around the clock to get it all done.

Never mind then, that the stage is so slick that serious thought is given to mopping it with Coke. Never mind that the time pressures mean that no opportunity exists for a full, on-stage dress rehearsal. Even in industrials, the show must go on.

And on it does go, gangbusters, like the D-Day invasion, and the audience is appreciative even laughing at the inside jokes about model numbers and such. But something odd becomes noticeable.

Though the nifty musical numbers get applause, it is the new cars that people crane their necks for.

It is the new cars that get the wolf whistles, not the slinky dancers.

Alan Weeks did get a big hand for his "Datsun Dazzle" dance routine, but that was nothing compared to what happened when a Datsun executive announced that the 810 Sedan would have a base price of $5,099.

And so even though "The DatsunDifference" would have to be judged a success for getting the point across one member of the audience announced afterward he was going to put another million dollars into his dealership - in another sense, in a human sense, there was an unmistakable note of poignance about that triumph.

It was almost a case of a job too well done, of the message, as advertised, making everyone all but forget about the medium that made it possible.