If they hadn't been singled out to sit on a bench from Ellis Island, microphones in their hands and a small crowd gathered around them at the Smithsonian's Folklife festival yesterday, these four people would have blended into the American scene as immigrants have always done - just another face at the office or the supermarket or picking up the kids from school.

But as they spoke of the circumstances that brought them there, of their flight from worlds in violent upheaval, their voices and tear-filled eyes betrayed emotions that native-born Americans are never likely to know.

"I always feel ashamed to leave my country," said Ilona Gyorik who escaped with her family from Hungary after the revolution of 1956. "It is like your house is burning and you leave your family inside." But it would not have helped to stay, she said, almost to herself. "It's like burning more of your family."

Minh Van Dang left Saigon in the last hours before Communist troops rolled into the city. He never wanted to leave, even though his work as a South Vietnamese policeman would have made him suspicious in the eyes of the new government.

"I'd prefer to stay in my job - in my career - to the last day of my life. But my wife and children were too afraid of massacre."

Minh's brother, family, had decided to stay in Saigon, and a Minh talked about him his voice broke through the microphone. "Now," said Minh, "he's in Hanoi, in reeducation camp, in jail."

For Saundra Summers life had always been hard in the Macedonian village where she was born. Her mother had died when she was a child and she was sent to live with a neighbor family, working as their maid from the time she was 5.

When she was 15 they had gone to the United States and wanted to bring her in as well. It was 1935. "I wanted to go there," she remembers. "We had the fear of the war all the time."

The only way she could enter the country was to marry an American, and the man her adoptive parents found for her was 45. She married him, bore his child, and lived in Buffalo, N.Y.

She said she was unhappy in her marriage; her respect for her husband did not make up for her feeling that she could not really associate with other Greeks or Americans.

When her daughter was 5 she left him only to find that her relatives in New York City would not accept her. "You can't come in," they told her, "you left your husband, people are going to talk, you give my children a bad name."

It was not until almost 10 years after she had come to this country that finally she married another man, a young second-generation Greek serving in the Army, that the United States truly became her home.

Yesterday, Summers set beside her mother-in-law, Helen Somertzopoulus, who first came to this country in the days when Ellis Island was still the nation's gateway. That was 73 years ago.

Somartzopoulus had come with her sister for the old American promise of opportunity, and finally had found it. "We came to America two or three years and go back - but we didn't make it that way. We stay here, and it look like we die here."

These four immigrants and other new Americans will be sitting in the Museum of History and Technology on the same bench - before the sepia, shadowy picture of Ellis Island - from 3 to 4 in the afternoon every day through Monday talking about the life that brought them here and the life they've led since.

They offer a uniquely accessible look at the population that has been coming to the United States at the rate of 400,000 a year in recent decision.

For most, mixed with the promise of a future in the United States is an ineluctable longing for the countries where they were born - lands to which some fear they may never return.

Even with the threat of Soviet troops nearby, Ilona Gyorik remembered yesterday, "When I crossed the border, I bent down and filled my pocket with Hungarian dirt." To this day she carries it in her pocket book, in a tiny silver box.