You could join the crowd surrounding Mick Jagger, president and chief executive officer of the Rolling Stones, or you could join the crowd surrounding Fred Silverman, president and chief executive officer of NBC.

Or, if you were Billy Murray, arguably the wackiest of all the whackos on "Saturday Night Live," you could, in your yellow satin baseball jacket, just hurl yourself pellmell at both of them.

"Heyyy - get outta here, you old maniac," sang out Murrary to a startled but obviously amused Silverman on the 64th floor of the RCA building. "Hey! This guy's a maniac and I mean it," Murray yelled. "Saturday Night Live" was celebrating the start of its fourth season and the fact that it has scored an enviable coup: the first live television appearance in a decade by the Rolling Stones.

"He's a very funny guy," said Silverman, patting his grayish hair back in place after wildman Murray had rumpled it into a tossed salad. Soon the zany cutup was off in another corner bumping buttinskis with a laughing and drinking Jagger, and singing "Respectable" with even less respectable lyrics than the Stones themselves had used on the program.

The appearance of the Stones on the show Saturday night was unquestionably, for the moment, the hottest ticket in New York. Building entrances were jammed with teeny-boppers, some of them not so short in the tooth, but then neither is Jagger. Security was quadrupled and the NBC pages, corporate cops and other assorted bully boys and bully girls were so adamant in maintaining a fortress against crashers that they almost threw NBC Entertainment chief Mike Weinblatt out on his ear. He was saved in the nick of time.

Among those who got in and managed to stay there was Our National Comedian, Steve Martin, who took great delight, after the program was over, in lifting cast member Dan Aykroyd up off the stage and holding him in the air. Watching from the crowd were singer-composed Paul Simon, Atlantic Records president Ahmet Ertegun, and director Steven "Close Encounters" Spielberg. New York Mayor Ed Koch, who opened the program, had arrived at the studio at 11 p.m. just after breezing through a nearby bar in time to see the Yankees win the pennant on TV.

The amazingly unassuming Silverman said this was the first time he had ever seen a "Saturday Night" show in person. "I have never done it before, and I will never do it again," he said, smiling. "You can see much better and hear much better watching it at home on television." His wife Kathy agreed. Silverman did not seem shocked by Jaggers ribald gyrations but admitted he was taken aback by a sketch on "The Battle of the Network T's and A's," a mythical NBC special featuring the bobbing breasts and derrieres of various movie stars.

Still, he did seem to find it funny. Heh-heh heh-heh-heh.

He also seemed genuinely delighted by the rambunctious Murray, who fears no man, even a network president, and has bosted how he applied "noogies" - tiny painless dents made with the knuckles of one hand - to the noggin of Silverman's predecessor, Herbert S. Schlosser.

"Herbie never even knew what hit him," gloated Murray in sentimental retrospect.

Between the show and the party, producer Lorne Michaels hosted a small gathering in his office to watch the tape of the concert portion of the program. This little conclave found Jagger, still in orange pants that resembled an inflated diaper, and Mayor Koch sitting side by side, with Jagger wondering aloud, "Maybe this wasn't such a good show," just as Michaels plopped the tape cassette onto the machine.

Much to the relief of Irwin Segelstein, Paul Klein and other top NBC executives who were also at the show, the live cameras did not fully capture two or three of Jagger's more sexually demonstrative gestures, such as grabbing a significant portion of guitarist Keith Richards' pants.

Koch sat watching the tape of the Stones with his chin nestled in one hand and a look of mild perplexion on his face. But when it was over he applauded like everybody else.

At the party on the 64th floor, a short time later, director Spielberg and cast member John Belushi traded hats and sunglasses. Belushi is known not to pleased when people mess with his hat. However, Spielberg has signed him for the lead in his new movie, "1941." Belushi is currenty starring in one of the year's top-grossing films, National Lampoon's "Animal Hosue," and his salary per picture has reportedly zoomed from $35,000 to $350,000.

And yet, unlike Chevy Chase, he has remained with the stock company of the uncommonly successful "Saturday Night" show, along with such other dabblers in the motion picture arts as Larraine Newman and Gilda Radner, both of whom were also at the party but neither of whom emulated the fashion style of the young lady who wore a 45 rpm record in her hair. She must have been from L.A. A lot of them were.

Belushi is not at all pleased with "Goin' South," a current movie in which he is briefly seen. He called the film "a piece of - " and said of the film's star and director, "Jack Nicholson is a total -, and you can quote me."

As he was changing clothes after the show, Murray heard a wardrobe man say, with great reverence, "Mr. Silverman is here." But Murray said, "Hey, I don't think he's got any spinoffs up his sleeve for me."

However, after buttonholing Silverman for around 15 minutes at the party, Murray emerged with a broad smile and in his best showbiz slickie voice, gushed loudly, "Well, he didn't exactly say the word 'spinoff' - BUT . . ." The ensuring pause was two months' pregnant. And then Murray himself spun off into the night, which did not end until RCA turned the lights up - like they do in a neighborhood bar - at 3:45 a.m.

It was NBC's way of saying, "Go home."