Three decades ago, Ronnie Gilbert's soaring contralto leaped from the Weavers' harmony like a bird in sudden flight. Carl Sandburg once said, "When I hear America singing, the Weavers are there," and no Weaver was more there than Gilbert.

Her stark black hair has long since turned to curling gray, but her eyes are clear, her skin smooth. The voice remains vibrant as well. Now in her late fifties, Gilbert still radiates from the renewal of the last five years. "Wasn't That a Time!" a prize-winning documentary shot at the Weavers' historic 1980 reunion, thrust her back into the spotlight she had abandoned 20 years before.

In the intervening years, Gilbert's work had been mostly in theater, with time out to earn a degree in clinical psychology. After the movie, she did a national tour with Holly Near, recorded her first solo album in two decades and has now embarked on a solo tour. It stops at Lisner Auditorium tonight, with Near as a special guest.

Not surprisingly, her commitment to music-with-a-cause remains intact.

"I come from a long, honorable tradition of political singers which goes back to the troubadors," she says. "My mom came from Warsaw, Poland, and she had an older sister who was in the union movement there in the early 1900s. My mother . . . spent a lot of time with her sister at union meetings, and music was a very important part of those gatherings."

It was a two-year stay in the Nation's Capital during World War II that connected Gilbert to folk music as a teen-ager. "I went to work in a government office . . . I was a rather shy and not socially accomplished person, so I was lonely. But I met wonderful singing people who took me under their wing and that's where I got my first experience."

Among those she met were Woody Guthrie, Cisco Houston and folklorist Alan Lomax. Soon Gilbert was dividing her time among work, studies at Anacostia High School (where she was almost expelled for refusing to participate in the school's minstrel show) and a fledgling folk group, the Priority Ramblers, who mixed war-effort songs with songs of social protest.

After the war, Gilbert moved back to New York, organizing for the Office Workers Union, working for the Textile Workers Union, eventually joining forces with several like-minded folk singers -- Pete Seeger, Lee Hays and Fred Hellerman -- as the Weavers. Theirs was a rare confluence of harmony and attitude, and thanks to songs like "Goodnight Irene," "On Top of Old Smoky," "Tzena, Tzena" and "Kisses Sweeter Than Wine," the Weavers became one of the most popular groups in America, bridging the gap between folk and commercial music.

The Weavers also became a target during the Joseph McCarthy era; branded as leftists and subversives, they suddenly could not get concert or television bookings. After one breakup and subsequent reunion in 1955, they hung on for another eight years, finally disbanding in 1963. At that point Gilbert moved into theater and that's been the focus of her art for the last 20 years. Much of her work has been with director Joseph Chaykin's Open Theatre and Winter Group, but Gilbert also has worked with Elizabeth Swados, Meredith Monk and Harold Pinter; and with Peter Brook in London and Paris.

In the early '70s, Gilbert moved to California. She went into therapy and eventually returned to school for her degree in clinical psychology. She started a therapy center in the Bay Area and eventually emigrated to British Columbia. "I lived in a remote rural community where I was the only game in town, which is what practically killed it for me because I had no resources of my own," she laughs.

Working mostly with parents and foster parents of difficult children in the mountains, Gilbert says, "I got my pioneer points . . . But I must have missed performing -- I told myself I didn't -- but there was something. The proof is that the very first opportunity I had to establish some sort of performing thing was setting up little theater games for my clients and anybody else who was interested. Before long I phased out my work as a therapist and went back in the theater full time." Gilbert's musical career has reblossomed since "Wasn't That a Time!" but the seeds were sown almost a decade ago when Holly Near dedicated an album to the woman "who knew how to sing and what to sing about." The Weavers had been a force in American protest music, but Gilbert, ironically, wasn't listening to much contemporary music. Her daughter brought her Near's record and Gilbert spent a day with it, she says, listening, crying, beaming at the connections.

When they finally met, "we could hardly talk to each other," Gilbert says. A generation apart, Near and Gilbert shared views on women's issues, nuclear disarmament, opposition to U.S. policy in Central America and other social questions. "And the first time we appeared together, it was an extraordinary experience," a communion that was evident in several scenes between Gilbert and Near in "Wasn't That a Time!"

"A lot of what the Weavers did was subtly political," Gilbert says. "When I think about the things we sang, especially on our records and in our public appearances in the commercial world, they were so mild. But the times were so awful."

Near will be Gilbert's guest tonight. "I know our association is going to be a fruitful one for a long time to come," says Gilbert, "but we really do lead very different lives . . .

"I think of myself -- and I know it's true of myself -- that I'm an ensemble player. That's why I like theater . . . It's an extraordinary experience that just touches every base you can think of -- your own ego, your sense of competition, your creativity. I like being tapped in that way.

"And the other thing is I get lonely up there."