As Conrad Martinez spoke into the microphone, the last three years disappeared and he was back in that moment: "Everything started shaking. Coming from California, I thought, 'This is an earthquake,' but then it didn't stop shaking. Then it kept on shaking. More and more, more and more."

Martinez, 42, worked for an Internet company in Tower One of the World Trade Center, in a converted old bank vault. He pushed open the door, he said, to a scene of people scrambling about and a cascade of debris outside the window, "just like the 1960s spy movies."

Everyone rushed to the fire escape. When he reached the ground floor, Martinez looked up at the tower. "And I notice something and I kept on looking, and I realized it was a person. And the person was wearing khaki pants, a dark tie and a blue shirt, and um, um, um, he landed and exploded."

Martinez remembered shaking uncontrollably. He sought counseling, but it didn't help. "That's probably why I'm here today," he said.

He was inside a miniature recording studio on the concourse of the train station where the towers once stood. The booth, which opened earlier this week, is the latest installment in a 10-year oral history project created by veteran radio documentary producer David Isay. He is gathering what he calls "American stories," and in other venues he has had grandchildren interviewing their grandparents and immigrants sharing their stories.

"There are a lot of stories related to 9/11," Isay said. "9/11 is one of the huge moments in the 20th, 21st century. You find a lot of stories coalesce around these big moments, the Depression, World War II, Vietnam."

StoryCorps received $550,000 from the Lower Manhattan Development Corp., the city-state agency charged with the rebuilding process, to construct the booth and cover initial costs. Visitors bring a friend or family member to interview, or a facilitator will pose questions. They leave with a CD copy of the 40-minute session. Clips from the project air weekly on National Public Radio; the full interviews will be housed at the Library of Congress.

Mary Marshall Clark, who oversaw more than 500 Sept. 11-related interviews for the Oral History Narrative and Memory Project, said the success of Isay's project will depend partly on whether people feel comfortable with the time limitation of the interview and the booth's location.

"He's asking the families to go to where their loved ones were destroyed," she said. "Many immigrants who suffered greatly in the political backlash -- will they want to go down there?"

Isay said the booth at Ground Zero is open to anyone to create an oral history but is primarily intended to offer "a sacred space" for families and survivors to pay tribute to their loved ones and to heal.

"It's a chance for families to remember not only what happened on September 11th but who this person was," Isay said. "The stories become the only thing that people can hold onto."

On a recent afternoon, people milled outside the booth, but many were reluctant to record their stories, saying they felt uncomfortable taking recording time from survivors of the attacks.

"I figure the people who deserve to talk are people who had some direct involvement," said Rick Ferrino, a business analyst who works across from Ground Zero. He was a student in Albany, N.Y., on Sept. 11, 2001.

For Michael Smith, his recording will be a legacy to his children and therapy for him. He was a fire marshal who responded to the planes' crashing into the towers. Smith, who is 46, retired a year later but has not stopped thinking about that day and the friends he lost.

He brought four pages of prepared notes to his recording session, but he didn't need them. He settled in before the microphone and began to speak in a thick Long Island accent.

"All you hear was this thundering train, and we said, 'What is that?' " he said. "You hear ba-boom, ba-boom and then loud thunder . . . all youse could do was look up, because all youse saw was, one floor, after the other floor, after the other floor."

After he had begun to run, he said, "I turn around real quick . . . all I see is this monster, concrete dust bowl coming up the street . . . and I ran into the side of the car and I got knocked down again."

"I was losing consciousness . . . a police officer and a marshal I worked with grabbed me by my shoulder, and the only thing I heard was: 'Is he dead? Is Smitty dead?' "

He wasn't. He survived, and now his words do, too.

Debbie Ang, right, from Hoboken, N.J., talks about her father during a recording session at the StoryCorps booth at Ground Zero.

Sarah Aguilar and her children listen to recording made at the studio.