"Age," says Joan Baez, "has never been one of my favorite things. I've never really understood what's so wonderful about getting older."

It can be hard on heroines when wars end with a whimper and intensity goes underground when the gray begins to glint in coal black hair and irony plays in the eyes that once contained outrage.

But right now it is back to the way it once seemed it would always be. Joan Baez is here with her guitar and a cause to pour her passion in. This time, though, she has infuriated a number of her former colleagues in the anti-war movement by charging the Vietnamese government with brutality. The weapons of choice, dueling newspaper ads, have continued since she launched the offensive last month.

She curls further into the couch in her room at the Madison Hotel, where she sits with her legs tucked up, birdlike. "People," she says as polished red nails flick the hair back from the wryest of smiles, "were always asking back then, 'What are you peaceniks going to do with yourselves when there's no war to fight?" And I always had some sort of pompous answer ready for that one until it happened - the war ended. And then I didn't have any answers."

The past is reviewed without self-pity, and instead there is a giggle and she remembers how differently this year began from the self-doubt and the guilt and the loneliness that had measured her steps since the movement splintered.

But it takes a moment to imagine Joan Baez, dressed only in a pair of blue striped socks, a pink scarf and her pacifism running down a California beach on New Year's Day, but that, she says, is precisely what she did, shouting to the wind and the waves that "this time I was getting the year by the horns and it wasn't going to get me."

So far, so good. This year she has a new record and a 22-city concert tour, but most important, she has an issue. "As long as I have a cause, something to put my energy into, it's all right. That's all I really need to get my adrenaline up."

Now she has stirred up a lot of adrenaline.

Now Joan Baez is asking questions of the Vietnamese government and the shards of the coalition that splintered when the war ended. Last month, she gathered together 83 co-signers and published an open letter to the Socialist Republic of Vietnam in five newspapers charging that "the cruelty, violence and oppression practiced by foreign powers in your country for more than a century continue today under the present regime."

Before the letter was published, she sent it out to a number of the disparate elements that made up the anti-war movement for their signatures. Daniel Berrigan was convinced, Dr. Spock was not - "That's all right," she said she told him, "I'll see you in the anti-nuke lines." Cesar Chavez signed the letter, Bob Dylan didn't get one. "Bob Dylan," says Joan Baez, "has never been involved in anything but himself since the age of 3."

And Jane Fonda wrote a letter back that managed to be both stern and rather odd at the same time. "Such rhetoric," she began, "only aligns you with the most narrow and negative elements in our country who continue to believe that Communism is worse than death."

And then the letter from Fonda concluded, "While I do not agree with your analysis and I worry about the effects of what you are doing, I still look forward to sharing in a dialogue with you. Your iconoclasm intrigues me and I wish we could understand each other more fully."

Baez is enjoying the irony of the charges being flung around her these days. It has come full circle, she says, since the day she made the front page of the Palo Alto paper at the age of 16 for refusing to participate in an air raid drill. "Ah, mon enfant terrible," said her French teacher, smiling. "What are you up to now?"

"I've managed to go 360 degrees," says Baez. "Then they called me a Communist. Now they say I'm an agent of the CIA. If my 10 years in the anti-war movement don't speak for themselves, then it's hopeless."

Her dark eyes look as large and luminous as they did when she captured the Newport Folk Festival in 1960, but now they belong to a 38-year-old woman dressed sedately in a purple blouse and flowered skirt.

For nearly 20 years, she has been an archetype of activism, singing the anthems of tortured times in the voice that seemed so pure in its passion, running like a clear stream over the jagged stones of the political riverbed.

She exercises that voice now, the upper registers that came so easily at 20 are more reluctant now. "I've always thought, 'Thank God, I have something to give' - I had nothing to do with it. It was a gift that I've tried to used for the things that matter."

And so she has been there, marking the milestones, inspiring the energy of the early years, soothing the wounds of the later ones. Seh sang for civil rights, and equal rights and human rights, for demonstrators and farm workers.

She sang at the funeral or Orlando Letelier and she sang for those in San Francisco who came to remember Harvey Milk. "I heard a young man in the middle of the crowd and he sounded so frightened. He kept asking, 'What will we do now? What will happen to us?'"

And sometimes when there is no answer, a lullaby will do, coming as it does from someone who has asked the questions so many times before.

Baez is not surprised that there should be such controversy over her actions among her former allies. "I appreciate the chance to make the distinction," she says. "Even when the war was going on it was clear that there was a difference between those of us who were anti-war and those who where anti that war."

She was not chagrined by the reports that the end of the Vietnam War did not bring an end to violence in that ravaged country. Her smile plays around the edges of the past. "I wasn't disillusioned," she says. "I've always saved disillusion and depression for my personal life.

"I met Bertrand Russell once when he was in his '80s and we sat in his little room and he served us tea. I said, 'All right, Bert, let's get on with it. What do you think our chances are?' 'Our chances of what?' he asked. 'Of survival,' I said. And he said that if people started turning things around in the next 20 years we could make it, and I asked what the chances of that were, and he said, 'Probably none.' So we laughed and ate our little tea cakes. And then you just get on with it. For me, it's all part of having had a Quaker upbringing. You tell the truth as you know it."

Now the truth again involves Vietnam, but it has been a long way from the night she sang on the balcony of a hotel in Hanoi while American bombs dropped around her and the concern that had her in a limousine at 8:15 in the morning heading toward Congress on behalf of the boat people.

She was terrified when the bombs fell, convinced she would die, but when the bombing stopped and the war ended there were other dangers. "It was disorienting," she says. "I felt guilty that I wasn't doing anything. Later, I read that Gandhi sometimes went for five years without being very active but at the time I really went into a slump." She was afraid to fly, afraid of heights, and lonely. Now, she feels, "it was a fear of death that was coming out - when you're really in physical danger, you don't have to invent things to be afraid of."

The war had seen the beginning and end of her marriage as well. Davis Harris was about to go off to jail for resisting the draft when she married him in 1968, and not long after he was released in 1971 they separated.

Her son by the marriage, Gabriel Harris, is 9 now and the delight of his mother. "I think I'm a good mother," she says reflectively. "That's what I would want for my epitaph - that I've been a good mother."

Soon she is attacking a lamb chop set among the gleaming china and silver and the Alpine linen of the Madison Hotel. "That's another thing I don't feel guilty about anymore - nice hotel rooms. I've found I like the comfort."

The comfort extends to the chauffered limousine that has taken her around Capitol Hill and which is waiting now to take her to a meeting of representatives from the local Vietnamese refugee associations. There is some talk of parking it two blocks away in deference to the desperate nature of the situation she is trying to help.

She is with her longtime friend and companion, Jeanne Triolo Murphy (with whom she has bought a home near her own home in Palo Alto in which to house refugees) and Ginetta Sagan, a small torrent of a woman who has long been active in human-rights issues and is the director of Baez' International Human Rights Committee.

That night, the limousine took the women to the meeting concerning the boat people.Most of the discussion is in Vietnamese, but the earnest testimonials, the intense look of the young calling for action not words, the patient smiles of the elders - they barely need translation. Joan Baez smiles and listens and, as the evening grows dark around the small group, they ask her to speak.

She expresses her support, and tells them how on her tour, she plans to make her own plea for the refugees to her audiences. And she tells them of the night the bombs fell in Hanoi and how frightened she was and then she gives them the gift.

She sang, strong and clear and sweet. And the exiled and dispossessed, the brown-robed Buddhists and the priests and the young who will not remember and the old who will never forget sat among the brass candlesticks and the red-tasseled lanterns and listened to her song. "And before I'll be a slave, I'll be buried in my grave and go home to my Lord and be free."

Afterwards, Joan Baez stepped into the dark cool night, tranquil. "The meetings never change, do they?" she said. "The questions are always the same." CAPTION: Pictures 1 and 2, Joan Baez, by Lucian Perkins - The Washington Post