Don't be alarmed. That aminous rumble of heavy-duty, industrial-grade promotion you hear clatering into town today is merely Paramount Picture's Christmas offering to the nation.

They're calling it "Saturday Night Fever," although "Holiday Profit Madness" might be more to the point.

Riding somewhere in the midst of this $6 million worth of film production, star-making machinery, record albums, books and assorted merchandising and promotional tie-in is a young actor named John Travolta.

He sports the most true blues since Paul Newman, the most profound chin dimples since Kirk Douglas and the most authentic Italian punk streetgeist since Sylvester Stallone, or possibly the Fonz.

And as if that weren't enough, Travolta dances. He struts around a disco floor with the arrogant grace of a Valentino. Yes, the movie also has disco music - by the big-selling Bee Gees to be specific.

How can it fail? All debts are covered. The movie opened at 726 theaters across the country Friday and all it lacked was a UFO landing. The 18-to-35-year-old disco crowd, so far untapped by Hollywood, is expected to attend, humming and shuffling its feet.

Lovers of struggling-sensitive-ethnic-working-class-youth films, a valued and proven market, are next in line.

Then there will be the pubescent and pre-pubscent TV set, all pestering their parents to waive the "Saturday Night Fever" R rating. For they are Travolta's first followers, addicts of the high-rated TV comedy "Welcome Back, Kotter" of which Travolta is not quite the star (Gabe Kaplan pre-empted the title role) but certainly the resident sex symbol.

Everyone concerned with "Saturday Night Fever" is hoping it will carry him across that big divide from tube to wide-screen stardom. Or that he will carry it across. Either possibility is acceptable.

So far the investment is looking quite safe. In its first three days at the box office, "Saturday Night," grossed slightly over $5 million, Paramount estimates $1 million already in the New York area alone. "It looks like it's running on the level of 'Godfather II," said Gordon Weaver, Paramount vice president of marketing. "It is a phenomenon. There are places where people are dancing in the aisles."

Weaver says that the promotional spending on "Saturday Night Fever" is "relatively modest," somewhat akin to "King Kong." In this case "relatively modest," means $3 million, which is as much as the movie cost to make. The promotion planning started a year in advance and that suddenly familiar Travolta-Rampant Poster, shot before the movie was filmed, went on sale Labor Day. Paramount didn't feel like waiting around for the two-week work-of-mouth time lag. "We wanted the phenomenom happening up-front," said Weaver.

The promotion encompassess not just the usual forms of advertising. There are "Saturday Night Fever" T-shirts, jeans, vests, decals, music books, cigarette, lighters and even a mirror. And of course there is a novelized version of the screenplay, published by Bantam Books. This kind of multi-level merchandising approach has been done before. The "Great Gatsby," "King Kong" and "Star Wars" also had tie-in fever.

But the hot item here is the music. The double-record "Saturday Night Fever" album by the Bee Gees began assaulting the nation's radio stations long before the movie's release. No less than four of its songs are bouncing around the Top 40 charts with "How Deep Is Your Love?" currently No. 1. Another $500,000 was spent on promoting the album.

Travolta plays a 19-year-old Brooklyn deadend kid named Tony Manero. He works for low pay in a hardware store, is held down by boorish parents and lack of opportunity - not unlike the Rocky syndrome. Tony's escape comes not from boxing at the gym but dancing at the local disco. On weekend nights, Tony primps, hotcombs and stands revealed as the Bee Gees doo dah to beat the band.

The producers tossed a party for the movie cast in Los Angeles a few weeks ago, taped it, syndicated it around the country as a TV special, and took out heavy newspaper ads to plug that. The music sells the movie. The movie sells the albums. The TV and radio and newspapers sell both. Round and round we go.

Travolta himself, meanwhile is going round and round the country with a cordon of publicists.They too are selling.

He zoomed into New York last week for a couple of days of frantic publicity parties. TV talk-show tappings and a press conference, then took off for more of the same elsewhere.

The press conference started an hour late in a suite in the Plaza Hotel - the excuse was heavy partying the night before, the publicists said. Travolta came in wearing a natty blue suit with a matching vest but no tie and his short open at the colar. He had brown western boots on.

Travolta's eyes, which usually are described in press reports as luminous, icy or diamond-like glowed warmly at each reporter or photographer in turn as he shook their hands. The eyes are seriously blue. The teeth are white, the hair wavy. Several of the press people melted under the strain and were unable to regain their cynicism for several hours. It was pathetic.

Travolta, like any actor who becomes associated with one character and then wants to stop being known as that character, has certain image problems. Since his Vinnie Barbarino on "Knotter" is associated with dumbness, some people naturally assume that Travolta is dumb. This quality was not in evidence at the press conference, although Travolta was not put to any serious test.

He presented himself there as a modest, thoughtful, boyishly sincere man of 23 - sometimes confident, sometimes nervous. How much of this is real is anyone's guess. Oh, and don't forget charming. Everyone agrees that Travolta is charming. On the screen it comes out charisma.

He said that he has been called arrogant, cocky and aggressive in some stories but was pleased to see that this trend appeared on the wane. In fact, he has taken to asking interviewers just how he is coming across to them. What else can they say? Charming.

Travolta says he isn't turning his back on TV, the medium that spawned him, but has just about had it with "Kotter." There have been reports of disagreements between Travolta and the producers, but he just says, "I've completed the character. It woul be redumdant to go back to it."

What dose he want to play in the future, "I'm looking forward to Tennessee Williams," he said.

But first will come the '50s rock epic, "Grease," already filmed this summer co-starring Olivia Newton-John. And next will come an as-yet-untitled love story to be filmed next spring in which Travolta will play opposite Lily Tomlin. He has a $1-million contract with producer Robert Stigwood for the three movies.

Stigwood, a native of Australia, has put together and entertainment empire in the past two decades, managing the careers of rock groups, then expnding into British theater and television and lately producing movies like "Jesus Christ SuperStar" and "Tommy." He also owns SRO Records, the label on which "Saturday Night Fever" was recorded.

As for Travolta, he says he's taking all the frenzy in stride. He's always wanted to be an actor - at least since the age of 5, he said. His mother was a high school drama coach who apparently infected him with the bug, and he quit high school to act at 16. Since then things have been going rather well. Does any of the marketing bother him at all? "Sometimes," he said. "It gets to be too much." The pressures? Sure, but he's not complaining. The John Travolta industry is having its best The John Travolta industry is having its best year.