The posters for the one-man show at the prestigious Olympia started going up on Paris kiosks early in June of 1981. By the end of the month, the three-month engagement was sold out. By October, when the accordion sounded its first plaintive note and the lanky performer with the familiarly rumpled face ambled onstage, ticket scalpers were having a field day.

After a hiatus of 13 years largely given over to acting, Yves Montand -- chanteur by trade and disposition -- was making his return to the music-hall. His old fans were out in force -- those for whom his renditions of "Les Feuilles Mortes," "Luna Park" and "A Paris" represent milestones in French popular culture. But the greater part of the audience belonged to the under-35 generation that knows him mainly as the star of such films as "Z," "State of Siege," "The Confession" and "Ce'sar et Rosalie." Even so staid a publication as Le Monde felt compelled to devote four pages to the phenomenon.

But Montand does not rest easily on his laurels. "As soon as I make my decision to return to the music hall, I don't sleep another wink," he says now that he's about to go before American audiences. "Because I know how much nervous effort it represents. I do not want to do a nostalgia turn. Myself up on a stage -- that's nostalgia enough. And I do not want to be fashionable. Fashions change very quickly. No, I just want to be myself -- someone who lives in the present.

"I was saying the other day that in my opinion, there are three things which do not age: a sense of humor, directed, if need be, against oneself; tenderness, because tenderness has no age; and a critical and lucid spirit. Perhaps I have always had them inside me, but as I advance in age, I realize their importance. A young man of 18 undergoes this extraordinary explosion of cells within himself that makes him think that after 40, life is over. That is not true, of course. Every day, a curtain comes down, but another goes up. Still, I think it is very important in judging yourself to retain the kind of severity you had at 18."

At 60, Montand is very much of the present -- an incontestable superstar in France, who embodies something world-weary but resilient in the French character. The lower-class kid, who made it big, but never completely lost touch with the people any more than he lost his meridional (southern French) accent. In the American imagination, however, which tends to simplify things French, he is generally defined by the women in his life: Piaf, already the glory of the French chanson when she took him under her deceptively frail-looking wing toward the end of World War II; actress Simone Signoret, his wife of 31 years and his occasional co-star; and Marilyn Monroe, with whom he had a celebrated affair in 1960, while filming, appropriately enough, "Let's Make Love" in Hollywood.

Montand knows it. Women are an integral part of his image abroad -- what he calls "the oo-la-la Frenchman." It is all Hollywood ever understood of him. But it also makes for good publicity, and when you're embarking on a worldwide concert trek, as he is, every bit of publicity counts.

Montand is still not sure how his three-month engagement at the Olympia escalated into one of those jet-propelled tours of the planet, usually favored by politicians and popes. But it did. He has just come back from Brazil. Beginning Tuesday, he will play a week at the Metropolitan Opera House, followed by engagements in Washington (Sept. 14 and 15 at the Kennedy Center Concert Hall), Montreal, Toronto, San Francisco, and Los Angeles. Then on to Japan. They're also clamoring for him in Rome, Milan, Helsinki, Oslo, Barcelona, Algiers, Madrid and Tel Aviv, but Montand says he hasn't yet decided if he will prolong his peregrinations.

"I put myself in jail with this tour," he laughs. "A golden jail. I close the door and keep the key. But still I'm inside."

Gilded bars notwithstanding, the tour represents an apotheosis for Montand, born Yvo Livi, son of an Italian peasant in a small village north of Florence. When he was 2 years old, the family emigrated to Marseille. By 11, he was laboring in the factories there. A hairdresser in his teens. More or less on a dare, he began his performing career in bars of doubtful reputation by imitating Charles Trenet and Donald Duck. And now . . .

Montand shrugs modestly. Of his one-man show, he says, "C,a vaut ce que c,a vaut." Which translates as, "It's worth what it's worth."

HE IS dressed this afternoon in a discreet pin-striped suit and his H black shoes shine like the hood of a new automobile. In his lapel is a Solidarity pin, given to him by Lech Walesa himself back in the the days when Walesa had a greater run of the world. Montand says he will wear it until Walesa is freed.

The Parker Meridien Hotel has cloistered him in one of its two-story beige aeries, overlooking a thunderstorm that just happens to be breaking in Central Park. Two locked doors separate him from the occasional maid scurrying down the thickly carpeted hall. It is a sterile decor, with its cool expanse of glass and modular furniture that could have been lifted from a Pinter play. The Mediterranean side of Montand looks out of place.

His English is -- at best -- game. At worst, impenetrable. When he can't find the right word -- or even the approximate one--he snaps his fingers rapidly, knits his wide brow, chastises himself for "being too lazy to learn another language" and retreats into French, before rallying for another assault on English grammar. The irrepressible expressiveness comes from his shoulders and his hands, which are invariably engaged in a supple pantomime of their own.

There is surely no irony intended -- merely indirect gallantry -- when he says, "I think the most beautiful pages about Marilyn Monroe were actually written by my wife in her autobiography, 'Nostalgia Isn't What It Used to Be.' For me, it is very simple. Marilyn was someone I loved . . . formidablement. I don't try to make excuses for myself. She was fantastic. At first, the two couples -- Simone and myself and Marilyn and Arthur Miller -- we know one another and talk to one another. But then Simone leaves for Rome and Arthur Miller goes back to New York. And I am alone in Hollywood, 39 years old, in full manhood. I don't speak English well and I have trouble making conversation. And the only person I know is Marilyn and director George Cukor. C'est tre s difficile pour monsieur. But if we go out to see a show together or if we go for a swim -- even though nothing has happened yet -- people talk. It was the same principle with Piaf. There was always a spotlight on her. If you were seen with her, you were automatically her lover."

Montand rejects Norman Mailer's thesis that he was the macho liontamer who, by cracking the whip, turned Monroe into a purring pussycat. "Not at all," he says. "I can understand that she was very irritating for some people -- especially other actors and directors. Sometimes it was the cameraman she didn't trust. Or the script. One day we come home from shooting and she says to me, 'You know something? I don't think Cukor is doing his work well.' I look at her and I suddenly see somebody who is frozen with fright, somebody petrified of the set, somebody who understands perfectly well that she cannot act drama or tragedy.

"And I say to her in my very poor English, 'Come on, Marilyn. Cukor has worked with Garbo, with Norma Shearer, with all the big ones. What you are telling me is that you are afraid.' For one second, there was this look in her eyes, at once confused and happy, like a child. Here is a foreigner, telling her the truth. Perhaps because we both come from the lower classes, she knows she cannot hide from me. She can hide from Arthur Miller. She can hide from Joe DiMaggio. But not me, because I have the key. She is afraid. But that brings us together. She understands that I need her to help finish my sentences. But she needs help from me, too. From this moment on, she is trusting. She is never late. And very proud of it."

For Montand, the recent speculation that Monroe was murdered is so much folderol. He saw her take pills to go to sleep after they'd come back from the set and wound down with laughter and champagne. And he saw her take pills to wake up. He witnessed the daily injections of vitamins that kept her going. "Then one night, perhaps because she can't sleep, she takes one pill, two, four or five, and that's it. You can't mix pills like she did. But murder? I don't believe it at all.

"She could be very depressed, and the real reason was that she knew she could not be a Greta Garbo or a Katharine Hepburn. What's more, nobody cared. No, we didn't care. Because like she was, she was a fantastic woman. It was not just her beautiful body, but her tenderness, her intelligence. Oh, she could act the idiot, but that is something else. She had le bon sens. That is more than intelligence."

THEN THERE was Edith Piaf. Montand's face, expansive even in repose, T lights up at the mention of her name. "The most funny woman I ever met in my life. I lived with her for two years and we laugh and make jokes all the time. She was very beautiful in 1944, not the woman you see at the end. And for that period of time -- two, three years maximum -- she could be the most pure human being. She kept to the man she loved and no one else. But always it was she who broke off the affairs. Never the man.

"Much later, I understand why. She needed always to be in love, because when she was in love, or imagined she was, she sang beautifully. And when she was breaking up with a man, and was very sad . . . she sang beautifully, too!" He laughs, and the laughter narrows his eyes to dots, while his mouth seems to stretch from ear to ear.

Legend has it that Piaf discovered Montand, but he already had forged a minor name for himself by then, singing ersatz American songs about cowboys and gangsters. "One of my numbers was 'Dans les Plaines du Far West,' written by a blind man, who, of course, had never seen a cowboy in his life. I sang a song called 'Je Vends des Hot Dogs a Madison and Great Central Park' ('I Sell Hot Dogs at Madison and Great Central Park'), which means nothing to you at all. I was very much inspired by animator Tex Avery and I would wear a cowboy hat -- it was cardboard, painted white -- or sometimes a vest and cigar, like Edward G. Robinson. At L'ABC, a Paris music hall in the summer of 1944, believe me or not, I arrive onstage looking like that, and I feel the audience going away from me like the ocean. I sing my song, and afterwards, for two or three long seconds, nothing. Then I hear a great roar. And I realize more than for my song, they are clapping for America and the Gary Cooper movies and the American troops who have landed in Normandy. Now I wonder why the Gestapo didn't arrest me, except that the Gestapo was too busy rounding up the Jews."

Piaf appreciated his warm voice when she invited him to fill out the bill with her at the Moulin Rouge, but she didn't much care for his repertory. "She says to me, 'Montand, I give you one piece of advice. Get yourself some French songs, if you want to last.' At first, I think she is crazy. But I throw away the cowboy song and the gangster song. She gives me her musicians and she even writes two songs for me -- 'La Grande Cite'' and 'Elle a Des Yeux.' And then I find 'Battling Joe' and 'Luna Park' and 'Lola,' which is like a little play in music. And I begin to make my repertory with that. I am so in love with her that I even try to sing like she does. When I go back to Marseille two months later, people are very surprised. They don't recognize me."

He pauses. "Do you know the first time I hear Piaf sing, I cry like a child. I want to take her in my arms, it is so beautiful."

THE MOST enduring adventure of his life, however, has been with SiT mone Signoret. Although the actress was married to film director Yves Alle'gret, shortly after meeting Montand at the Colombe d'Or restaurant on the Riviera in 1949, she took took up with him. "We had been struck by lightning," Signoret later wrote, "and something indiscreet and irreversible had happened." They were married two years later.

Sometimes, their professions overlapped. They appeared together on the Paris stage in Arthur Miller's "The Crucible" and shared billing in such films as "Is Paris Burning?" and "The Sleeping Car Murders." She came up with the idea for "Le Te'le'gramme," one of the crowd-pleasers in his concert, in which he dictates a billet-doux to a bored telegraph operator. But mostly, they have kept their careers separate, which is one reason Montand believes they have remained together.

"In a way, we take great delight in dazzling one another with our work," he says. "But Simone is someone who never put her personal ambition before what I call her fullness as a woman, her ple'nitude de femme. I can understand that a woman is ambitious. But I know lots of actresses who sacrificed everything for their careers and now they are sick and dry. Of course, you cannot do this kind of work without giving it everything. Simone had two miscarriages. Both times she is making films. And the emotion she brings to her work is so big, so intense, that she loses the babies.

"But the minute you finish the work, you must close the door. Walk away from it and live like a human being. Don't rush out to find out what the newspapers say, what the critics say. Basically, we are all narcissists -- you me, everybody. So don't develop the narcissism. It's too dangerous. Ingrid Bergman was one of the rare people who understood this. So does Simone.

"Naturally, passion does not last forever. It is inevitable that one day it dies. Then you love your partner, but you are not in love. Simone and I have had our moments of rupture, when it all could have gone to hell. But we have always left the door open for one another. And I was always happy to come back to my wife."

The marriage even rode out "l'affaire Marilyn" and the kilometers of copy it inspired in the popular press at the time. "The one person in life I didn't want to make any hurt to was precisely Simone," he says. "She was very sad. I pay a lot after that, but mostly it was de bonne guerre. In good sport. It's okay. I understand. I bend my back. I am patient. After a while, Simone doesn't talk about it any longer, but sometimes a glance can be more important than the word. Then one day, I say, 'Enough! Do you want me to take a pencil and paper and write down everything that happened?' And it was over. Finito. Simone was really fantastic through it all."

Signoret recently underwent a pancreas operation, which has prevented her from accompanying him on the sundry laps of his world tour. "She has lost a lot of weight," he says, "and she looks great. Because around the time of 'Madame Rosa' 1977 , it was different. I don't ask for a woman who has become old to look like she did when she was 18. But for her to destroy herself, I don't like it. It's not fair for her, but it's not fair for me, either. We live together, after all. I tell Simone this and she understands."

Montand beams. On the whole, he says, "c'est une ve'ritable histoire d'amour."

FOR SEVERAL decades, Montand and Signoret were among France's most F ardent and visible leftists, apologists for the Soviet Union, despite a personal life style that was anything but proletarian. In 1950, they both signed the Stockholm peace petition and it was no accident that their production of "The Crucible" in 1954 drew pointed comparisons between the Salem witchcraft persecutions and the trial of Julius and Ethel Rosenberg. At the height of McCarthyism, they were turned down for visas to the United States -- an injunction that stood firm until 1959 -- after they refused to say whether or not they had ever been members of the Communist Party.

Although he was an outspoken opponent of the Vietnam War, Montand says he has come to rethink certain political tenets he held in earlier years. "I come from a poor family and I grew up fighting for something to eat. At that time, it seemed very simple and clear: Marx was going to solve everything. He had replaced God. There would be happiness and food and no more prostitutes. Man would be perfect. This faith, we needed it to survive.

"In fact, we don't need it. That kind of optimism and hope at all costs is a danger. It is very important to see things as they are. Already after World War II, the issues are not so clear-cut. But then the enemy was Nazism and it blinded us to what was really happening in Russia. Some people, like my friend Jacques Pre'vert tried to warn us. He told me, 'I have been there. Beware.' But I refuse to understand. In my mind, he's a very nice man, but he's a poet. He doesn't understand the revolution. Even in America, the intellectual writers make the same mistake.

"I have to wait until 1956 and the Russian invasion of Budapest. It was a revelation to me. I realize that to condemn only the West and to let the East off the hook is too easy. To talk about the trial of the Rosenbergs, but not the trial of Slansky a Czech party official hanged in 1952 for revisionism and Zionism , that is not fair. Okay, we know what goes on in El Salvador. But at least the people in El Salvador can vote. Can they vote in Poland? Romania? Cambodia? Cuba?

"I am still against unbridled capitalism, yes, because it's very destructive for the nation. But I believe in a sane capitalism, capitalism with controls. No, I cannot condone McCarthyism or the Vietnam War, and we know what happens in American jails. But we must defend the American constitution and American democracy. Even in the past, I say this. We must fight every day to give more democracy, more freedom. The people of the left think there is only one philosophy, one truth. That is monstrous. The truth is multiple. We should hold onto our illusions, perhaps, but not our certainties. We can dream, but our dreams should not be utopian."

Montand furrows his brow. He's not sure he's been making his point. He doesn't want it thought that he's recanted his former political fervor. Or that age has turned him into an establishment bourgeois, which is one of the pitfalls of being a Frenchman. Suddenly, he resorts to a poem which Pre'vert wrote for him 15 years ago and which has since been set to music as part of his concert.

He recites it in French and his voice sounds like warm honey:

"Signed up against my will/ in the mill of ideas/I didn't punch the clock./ Drafted as well into the troops of ideas, I deserted./

"I never understood much about things./ There aren't many things to understand, big or little./ There's something else./ Something else -- that's what I love, what pleases me, what I do."

It is, one gathers, his credo.

THE thunderstorm has lifted and gray afternoon light is filtering through T the windows. Montand is asked what ambitions remain, now that he is at the apex of his stardom.

"I don't want to be a saint," he reflects. "I am what I am, with all my contradictions. I try to be firm, knowing that I am never 100 percent sure of what I am saying, even now. I want to be up to the task. And I try not to be too much of a bastard. Notice I didn't say I wasn't one. Only that I try not to be. Voila."