Movies as jovial as Jean-Charles Tacchella's "Cousin, Cousine," one of the big hits of 1976, and "Blue Country," which has just arrived at the K-B Cerberus, lead one to anticipate a rather jolly creator. Somebody big and expansive. Maybe Willard Scott with a French accent.

Tacchella has the accent, and it's a charming one, but he could not be mistaken for Willard Scott's French cousin. Small of stature and rather saturnine of countenance, Tacchella turns out to be a reserved, thoughtful, middle-aged gentleman, pleasant but not irresistibly festive. One would not immediately identify him as a film-maker whose work suggests that life is basically an ongoing wedding party, picnic or heavy date.

Tacchella, and his wife, a diminutive, pixyish character actress named Ginette Mathieu (she had a bit role in "Cousin, Cousine" as a flustered party guest and plays one of the principal roles in "Blue Country") were stopping off in Washington for the first time.

The American success of "Cousin, Cousine" had not taken him by surprise, he said. The mystery was the failure of importers to pick it up sooner. "Oh my first trip to America," he said, "we show 'Cousin, Cousine' to college students. It was very popular. In New York, in Los Angeles, in Berkeley. Every place we go, the people are pleased with the film. Then we returned to France and for six months, no offers. Finally, a deal is made, but I think it was better for the American distributor than the French producer."

Tacchella did not have a financial interest in "Cousin, Cousine" himself. "It was only my second film as director," he signed. "I was not able to make such demands. If I had known, maybe I work for free, but at the time, who could know?"

Tacchella denied a legend that had evolved in the aftermath of the film's success: French audiences were indifferent to "Cousin, Cousine." Tacchella insisted that, on the contrary, the film was a great success everywhere, including France. "We have in Paris big theater complex," he said. "On the first day 'Cousin, Cousine' played in the smallest theater. Two days later it must be moved to a bigger theater. By the end of the week it is playing the biggest theater. The difference is that in France the film was one French film among other French films, all of them popular. In America 'Cousin, Cousine' became unique. There were no French films as popular for many years. It is different circumstances, but people everywhere like the film the same."

Tacchella and his wife maintain a residence in Versailles but prefer to spend most of their time at a renovated country home in the Haute-Provence, the region in which "Blue Country" is set.

Tacchella worked as a journalist and movie critic for a number of years before launching an extended career as a screenwriter in the mid-'50s. "In 1962 I said I've had enough!," he recalled. "I left Paris to live in a house in the blue country. I was trying to become a director, but I could find no one willing to risk the money. I had to earn my life writing TV. After years of movie writing, maybe 70, 80 screenplays, I switched to years of TV writing, mostly serial shows. In one year I set a record of 120 hours. But all the time I think of directing. It took another eights years. I found a producer for a short film. "The Last Winter," a love story about a man 85 and a woman 79. That was in 1970. Three years later I directed 'Voyage en Grande Tartarie,' my first feature."

Tacchella's new film grew out his fondness for the region in which he resides. "It is the country of Jean Giono," he said. "Many years ago Marcel Pagnol and Jean Renoir made films there, and I wanted to make one myself. I am a man of the Cinematheque, a man of the cinema clubs. But my film must be about the country of today. It is much as you see in the film, with people from the city who want to settle in the country and country people who want to go to the city, and always somebody is inviting the whole village to a party."

Tacchella's films have an improvisational air, but the filmmaker himself dissaproves of improvisation, which he feels can destroy the rhythm of scenes. After devising a story line, Tacchella likes to cast his films, socialize with the actors and add details tailored to the personalities of the performers. "For example," he said, "when I meet Victor Lanoux for 'Cousin, Cousine,' he was excited about his new motorbike Japanese. So I think, it would be fun to include this motorbike. Marie-Christine Barrault told met that when she is in love with a man, she likes to cut his toenails.I can use that too.

"In 'Blue Country' the comedian Jacques Serres likes all the time to fight. I know this about him. So I think, it would be funny if he goes to the wrong floor of hotel and begins fight with the wrong man, hat sort of detail The small scenes I put in to help the comedian. I am against improvisation and against indentification of audience with one character. Always my ambition is to change the mood of a scene, to go form one sentiment to another sentiment.

"I agree with Cheknov. He said about his characters, I did not accuse everybody, I did not acquit everybody. We have always a good mood on our films, and the actors know that now. On the last day of shooting 'Blue Country,' no one wants to leave. Some actors say, 'Let's have a drink to celebrate." We had drinks forthe next threenights. The movie was over, but everyone wants to keep celebrating. So you can see, themood with us was good."