"I haven't quite got that main theme," says Joseph Sargent, director of the movie, "MacArthur." He tries to whistle a few notes, but he can tell by the pained expression on composer Jerry Goldsmith's face that he hasn't quite got it indeed.

"No, no, it's like this," says Goldsmith, who correctly counter-whistles the instantly addictive march he wrote to open the film and bring the audience to attention. "Oh, yeah," says Sargent. "Right. Sure." Goldsmith smiles patiently.

Two hours earlier he'd conducted the same music with 70 musicians in a crowded recording studio while silent troops passed in review for Gregory Peck on a movie screen at the back of the hall. Peck plays Gen. Douglas MacArthur in the $10 million Universal military biography to be released next month.

It may seem anachronistic in this computer and synthesizer age, but an orchestra or real live people still has to get together and serenade a movie screen in order to add music to movies. In about 40 years, the process has changed little; the musicians play while the conductor conducts and watches the film, section by section, on the screen behind them. Advanced electronics and stereophonic sound have, however, introduced a frustrating slew of technical refinements and complications.

So that today a man like Goldsmith - easily one of the top five working movie composers - has to be no only composer but technician. Things aren't quite the way they were when such illustrious pioneers as Max Steiner ("King Kong," "Gone With the Wind") were creating the art of the film score.

"Steiner only had one lever to worry about - it went up for loud and down for soft," says Goldsmith, standing in a control room worthy of a sci-fi movie. "Today, there are dozens of levers. I've learned all. I can about this stuff so that the engineers can't snow me."

When the 70 musicians play - for wages of about $125 each per day - the music for "MacArthur" is picked up by 37 microphones stashed around the hall and fed into 16 different audio channels which are then mixed down into three basic channels for recording onto film. Because there will be stereo as wellas monaural prints, all the music will have to be mixed twice.

The final mix, later, will combine the music with all the other sounds in the picture, including mere words spoken by actors. "There are times," says Goldsmith with a grin, "when you want to hear the dialogue."

Goldsmith has scored more than 65 films, demonstrating spectacular versatility - from the lush plush "musicnoir" of "Chinatown" to the dissonant panic of "Planet of the Apes" to the lavish romanticism of "The Wind and the Lion." He was anxious to score "MacArthur" even though he's already done a General movie, "Patton." He says, "The hard thing with this picture is to top 'Patton' and still be, you know, different."

He is assured several times throughout the day that the march for "MacArthur" is even better than the march for "Patton." Usually when told that he just gets a worried look on his face as if to say, "Well, I don't know about that."

This year, after eight nominations, Goldsmith won his first Oscar, to honor an inventively hair-curling choral and orchestral score for "The Omen." He'll score "The Omen-2" next year. The Oscar has taken its place on a mantle near Goldsmith's Emmys (for "The Red Pony" and other TV scores), and Goldsmith says he's surprised at how many visitors insist on fondling the Oscar statue.

Goldsmith, 48, is dressed for this work day in Hollywood-sloppy-chic - baggy beach pants he keeps pulling up and a pullover drawstring top. He has a softly craggy face that somehow suggests both Dustin Hoffman and Johnny Puleo of the Harmonicats. You can tell Goldsmith hasn't let Hollywood make an android of him by the way he takes a compliment; he shields his face or blushes. His eyes may water. He looks away.

This can be interpreted as an indication that Goldsmith's music, in that very old phrase comes from the heart .

In the recording studio, however, it must go from the heart into 16 channels, and for "MacArthur," this has been difficult. A "technical malfunction" has required that all 34 minutes of the original score, plus 15 minutes of such "source" music as Chopin's Funeral March (for FDR's funeral), be redone, It took 20 hours the first time; on this day, Goldsmith is about halfway through the rerecording.

The day starts at 9 a.m. and, when it ends for the orchestra at 1 p.m., Goldsmith will be told by an assistant that he has recorded 12 minutes of music. "That's not bad at all," says Goldsmith. "That's not bad at all for four hours."

The musicians are recording the main title march, the music that accompanies the credits for the film, over introductory footage of MacArthur and cadets at West Point. The march is only 2 minutes and 14 seconds long, but it will be done over and over until Goldsmith gets the sound he wants. He does not get the sound he wants until Take 14.

With his balloon of fluffy gray hair making him clearly visible, Goldsmith stands on a platform at the center of the room, behind a large easel that contains his sheet music and an electric timer. The musicians are cordoned off into sections by moveable baffle walls. Very few of them can see the screen.

Before each take, there is a loud ticking sould through the hall. The musicians can hear this even as they play, through one-ear headphones they all wear. "It's the cueing system we use," Goldsmith explains later. "The click track. It works like a metronome, so that the music can be precisely timed to the picture. Before we start to record each section, you hear hour warning clicks - sort of like Lawrence Welk saying, "Uh-one, uh-two, uh-three, uh-four."

There are also visual signposts for the conductor, gouged right into the film - "streamers," which are white lines that scamper across the screen before music is to begin, and big white dots, keyed to similar marks on the conductor's sheet music, that signal a change in tempo or mood. The film used during scoring is a scratched and tattered, black-and-white, silent work print.

Each section of music recording begins with Goldsmith calling out a number that refers to a part of the score; the main title's number is M-901. He taps his baton as the lights go down and the projector starts spitting images onto the screen. The first sight is, in this case, the Universal logo. The first sound heard is a mallet striking the strings of a piano in a portentous rhythm: DUM, da da dum, da da dum dum dum da dum . . ."

Two things happen after each take. First, Goldsmit grabs and lights a cigarette, and second, he runs off to the control room to listen to the recording of the take. More often than not, he comes back out and the whole thing is done again.

To the engineer in the control room, Goldsmith will say, "I want the feeling of the field; I want that vast feel." To the musicians, he will say things like, "Can I have a little less celli a the beginning?" and "Strings, take it a little easier so I can get the oboe out." To no one in particular he will say, suddenly hobbling from the podium, "I've got a cramp in my foot and don't ask me how I got a cramp in my foot."

During a break, Goldsmith talks about the tricky craft of scoring for films. The hammer on the piano strings, he says, will be a repeating motif throughout the film. "It's just a gimmick, really. It's strange, because the simplest gimmick - the most musically simplistic kinds of things - can work very well dramatically in a film. Then you'll turn around and write something fancy in double counterpoint that sounds marvelous musically, and it won't work at all.

"There are times when you can be too musical for a scene dramatically - you run the risk of overpowering a scene. No, you can't save a scene with music, but you can sure help. I've said many times, great pictures have saved some bad scores, but great scores never save bad pictures. I can write a brilliant score, but if the film flops, I'm going down the tubes with everybody else."

Snobs have been known to dismiss movie music because the creative options are limited by the construction of the film. Goldsmith says if this were the 19th century and there were no movies, he would still be writing music, and he sees no shame in being part of a commercial enterprise. "Rossini, you know, was a very wealthy man. He just kept cranking out operas and getting richer and richer. And Mozart needn't have starved. He just couldn't hold onto his money."

If they were around, they might be writing film music today, says Goldsmith. "If Wagner were around, I know he would be writing it."

Hollywood composers have never been known as members of a particularly friendly fraternity. There is intense rivalry by tradition. The system somewhat encourages this. Producers and directors really hear a score for the first time when it is recorded with all those expensive musicians. If they don't like it, they don't ask for rewrites. They throw it out and hire another composer. Two of the films Goldsmith scored - "Chinatown" and "Seven Days in May" - were written after other composers' scores were rejected.

Still, not all composers hate each other. Goldsmith says his good friends include composers Alex North ("Rich Man, Poor Man") and John Williams ("Jaw"), "We get together and play chamber music," he says.

Back at the recording studio, Goldsmith is in the control room to mix Take 14 of the main title. It takes about half an hour to diddle around with the 16 audio tracks and get a balance that sounds just right to Goldsmith.

He wants more "bottom" (bass). He wants less brass. He wants reverberation on the electric flute. All this is done with knobs and levers by the engineer. Finally satisfied, Goldsmith puts the reel of tape under his arm so he can go and play it for the film's executive producers, Richard Zanuck and David Brown. Normally this would be a simple matter of walking a few feet. But Goldsmith has been recording not at Universal but at The Burbank Studios, a few miles away.

There weren't any recording studios available at Universal because of heavy TV series production there. So Goldsmith has to get into his Porsche and onto the Hollywood Freeway. The producers hear the recording. They like it. Goldsmith returns to record more snippets.

Later in the day, though, Goldsmith plays the very same main title tape again, back at Universal where Sargent is supervising the sound effects recording for the film. This time, the tape sounds awful, radically different than before on this different set of speakers. In fact, the countermelody somehow staged a coup and is subjugating the melody.

The took on Goldsmith's face suggests he would rather hear Sargent whistle the whole soundtrack than suffer through this. He groans. He slaps his forehead in disbelief. He will have to record the whole march over again, or at least completely remix it.

"Nothing is easy," he'd said to a friend at lunch in the Universal dining room.

"Not in the movies," he guy replied.

There's at least one thing about scoring films that makes it a unique part of the filmmaking process: An outsider can watch it being done, be told and amazed by it. Maybe it's one of the last bastions of magic in the movies.

Jerry Goldsmith can tell himself that as he records M-301, Main Title for "MacArthur," Take 15.