ONE EVENING about two weeks ago, when comedian and pianist Victor Borge was 10 minutes away from the intermission in his show, playing at the Imperial Theater in New York City, someone in the audience shouted, "There's smoke coming out on the stage!" Without even looking up, Borge shot back, "Oh that's part of the act. Don't worry about it. I'll play Handel's Water Music."

"I knew I must not let a panic develop in the theater," Borge recalled a few days ago. He will be appearing at the Kennedy Center Opera House this week with soprano Marilyn Mulvey. "Already a few people were getting up to go out. So I told them to sit down, it was all part of the show. When I looked up, sure enough, there was a lot of smoke coming out around the lights. But I saw one of the theater managers standing in the wings and motioning to me that it was all right, that they knew what the trouble was and that there was no danger.

"But before the intermission arrived," he said, "the whole theater was full of smoke. By then, people were laughing their heads off. They thought it was very funny. It was a good thing that the smoke was chemical and not from a real fire. Actually, we found out that someone outside was filming the movie, 'Wiz' right next to our theater, and they were blowing the smoke the way it blows in the cigarette ad on Broadway. Only it was all blowing right at us."

That story is only one illustration of what Borge means when he says, "Every performance includes the audience, the environment, and anything that happens." Fortunately it does not always get quite so melodramatic. The day of his press conference at the Kennedy Center, Borge called attention to the Waterford crystal chandelier in the south lounge of the Opera House.

"I wonder where they got that chandelier," he mused. "It tinkles in F. A chandelier in F. Hmm." Short pause. "We have six of those in our house." Pause. "In the breakfast room."

Someone asked the Great Dane if it was true that he had had it with the birds. Instantly he shot back," I think they have had it with me." The birds in question were the Rock Cornish hens that Borge began raising and made into a gourmet hit some years ago when he bought a big place in Connecticut. It had been a game preserve but he said, "I did not want all that shooting going on around our children." (There are five.)

"I started raising the Rock Cornish hens for fun. But it very quickly got bigger and bigger. We were reaching the point where we could process 3,000 birds an hour. There were 125 people working in two shifts. And it took more equipment and more machinery. And the money kept going out faster than it ever came in. The ideal size and weight hen was 16 ozs. But when you hatch 10,000 hens you cannot always guarantee that each one will be exactly 16 ozs. And places would order the birds, but if they were 17 or 18 ozs, then the people would only pay for 16 ozs." So Borge sold out.

"Have you always combined comedy with your music?" is a question invariably asked of Borge. "My teachers thought I did," is his fast reply. But talk to Borge about his background, his childhood, and his musical training and you find out how it happens that he plays the piano as beautifully as some of the big names of the present and past. Only watch out. Every Borge line is likely to mix truth and humor in equal parts.

"My father played under Wagner at Bayreuth," he began his explanation. "And he played in the opera orchestra in Copenhagen where we grew up. He played there for 35 years. When he came home my mother hardly recognized him." When I was a child I played the piano a little, but then I was taken to Vienna to study, and finally to Berlin where I studied with Egon Petri." That's an impeccable pedigree for any pianist.

"A few months ago I conducted in the Tivoli Gardens in Copenhagen in the theater where my father played in 1880. I have played there many times. This time I was made an honorary citizen of Copenhagen. They gave me a baton which the King of Denmark had used when he conducted there."

Orchestral conducting is something Borge does a little more each year. Some years ago, one of his friends, Benno Moiseiwitch, a great British pianist, asked Borge to conduct a concert in which he was going to play two Rachmaninov concertos. But Borge said he declined. "It would not have been right. People would not then have taken it seriously." As a conductor, however, he has become one of the top attractions of the Romantic Music Festival held each year on the campus of Butler University in Indianapolis.

I was there last spring and admired Borge as he led the Indianapolis Symphony in works for orchestra alone and then in the more complex business of accompanying violinist Aaron Rosand in a concerto. He handles the baton with complete ease, as people know who saw him with the National Symphony last summer at Wolf Trap.

Borge has a solid theory about why his shows keep on working as they do, even when, as he says, he uses material he has used for years. "I'm not bound by any limitations," he explains. But just to be sure, he tapes every performance and checks to see what works best with his audiences.

Victor Borge first came to this country in 1940 after Denmark was invaded by the Germans. He was playing in Stockholm at the time and simply never went back. "For some reason," he says, "I had landed at the top of the Nazis' Public Enemy List. I don't know why. Perhaps it was because I used to tell people who asked me the difference between a Nazi and a dog that the Nazi raises his arm."

When the Steinway piano people in New York saw his credentials and clippings, they gladly gave Borge permission to practice on the pianos they keep in their famous basement where artists go to use and choose. Borge says that one day while he was practicing, a gray-haired man kept opening the door, looking in, nodding his head in approval, and closing the door again without saying anything. "I thought it probably was the janitor."

Several days later, Uncle Billy Steinway, the patriarch of the family firm, said to Borge, "You have an admirer." "Oh," replied Borge, "that's good. I'm glad someone likes my playing." "Yes," answered the Steinway chief, "that man who has been looking in on you is Josef Hofmann. He likes your playing." Hofmann was one of the greatest pianists who ever lived, and at that time, the head of the Curtis Institute in Philadelphia.

Sometimes while listening to Borge the comedian it is hard to remember how beautifully he can play. After all, he can convulse listeners by announcing that he will play "Hemorrhage - no - Humoresque." Whereupon he launches into Dvorak's world-familiar piece, only somehow it comes out in two keys instead of the staid G major in which Dvorak wrote it.

Meanwhile the gags are running full steam ahead. "I'm doing an article for Playboy magazine. Maybe it will land me in the White House. Yes, it's true, the Boesendorfer does have six more keys than the Steinway. The Steinway has 88. Steinway also has three sons. Because of the extra keys on the Boesendorfer, which are sometimes white and sometimes black, pianists who are used to having the center of the piano right opposite their middles are off center at the Boesendorfer - because of the extra keys. I was frightened of the extra keys at first."

For years Borge has frustrated his listeners by playing only the beginnings of endings of pieces. A few measures off either end. For most of those years he has refused to play the final chord of Rachmaninov's C Sharp Minor Prelude. Last Monday when someone begged him to, he played it. All by itself, a lonely C Sharp Minor chord."I play only the ends of pieces because President Carter has asked us to save energy," he explains.

As the C Sharp Minor chord faded away, a TV man brought a light meter up close to Borge's face. Shying away from it, Borge exclaimed, "Oh, I thought he was an ear specialist." When someone asked him how he reacted when he was compared to the late Vladimir de Pachmann, the instant rejoinder was, "I would rather know his reaction. After all, he was one of the giants. And now look where he is. I would like to be able to play as he did. And now I guess he would like to be able to play as I do."

A troubled look comes over his face. "Last week in New York I saw a notice in my hotel bathroom that said, 'Please place curtains inside tubs.' Why do they have to ask the guests to do that? Don't they have enough help in New York? It took 28 minutes to take off all those little rings and put the curtain inside the tub. And besides, they don't tell you which curtains!"

Borge has a very personal view of our language. He says that anyone who learns English has a different slant on it from those who grow up with it. "Just look," he began on the subject. "you say that Ignaz Friedman sat UP all night, writing Viennese waltzes. Then you say the next morning he sat DOWN to breakfast. Why?"

To speak of Friedman is to bring up one of the greatest moments in any Borge show. You never know, but if he feels like it, he may play not only the opening, or the closing, but an entire piece, every note. And if you are lucky, it will be one of the Friedman waltzes. At that moment you will be hearing someone play with the kind of style and graceful elegance in his playing that people used to associate with Hofmann, Moiseiwitch and of phts, psts, thrrrmm, and ssts as Borge does his infamous punctuation routine. That could even come as an encore.