Almost two years ago, singer Miriam Makeba, whose lyrics and life reflect Third World struggles, performed in Lesotho. That appearance in a nation locked in by her country of birth, South Africa, was the closest she has been to her home in more than 20 years.

"It felt good, for a change, to address an audience in your own language. Of course there was also a sadness, when you look across the border and realize that is the border and that our umbilical cords are buried on the other side. It was kind of a sweet-and-sour feeling," recalls Makeba.

Makeba, who prefers to be called a "realist" rather than a "protest singer," is performing tonight with the master jazz drummer Max Roach at the Kennedy Center. This, her first concert tour of the United States in l0 years, has been organized and produced by the New York-based South African Students Union. It was her strong allegiance to the students that prompted her return to a country that once rejected her and her politics.

"The students certainly didn't need to convince me to return, as a mother, as an artist. They need my help, they can have it," says Makeba, who had her South African citizenship revoked after her appearance in an anti-apartheid film. She speaks in whispers, more from fatigue after a night of traveling than from any hesitation about her purpose. The fact that the tour coincides with her 50th birthday next month prompts a coyness that usually doesn't surface in her conversations.

"I don't know about this birthday. I think I should slow down," laughs Makeba, who lives in Guinea, spends more than half the year touring and is finishing work on a film about South Africa. There are few signs of age in her small, taut face, gently framed by gold-decorated braids. When she sings a thunder explodes from her short, robust form. On Wednesday night Mayor Marion Barry and Lettumplay, a local arts group, honored her at a party and she sang her thanks with an old song that expresses the life of many exiles, "I Walk Alone."

In a song entitled "West Wind," Makeba sings: "Make us free from exploitation and strife/because nothing is more precious than life/West wind with your splendor take my people by the hand/Spread your glory sunshine, Mother Africa, unify my precious land."

When she lived in the United States in the 1960s, she already was an internationally known singer, introduced to America by Harry Belafonte and Steve Allen. In turn, she introduced the South African languages and legends of Xhosa and Zulu in vibrant, haunting songs. Her departure in 1968 coincided with her marriage to Stokely Carmichael, now called Kwame Toure, who gave much of the black power and separatist movement of the late '60s its ideology and charisma.

"I had decided to leave anyway because I felt I was missing Africa. I had been away from Africa 10 years, long enough. But at the same time, I married Stokely and all of a sudden concerts were gone, records disappeared," says Makeba. "I decided not to fight--to concentrate where I didn't have any harassments or any problems, where I could just perform."

What happened during the 10 years she and Toure were married, any glimpses of the love that brought them together and the changes that pulled them apart, is private. "No, when you love somebody, you didn't think of things like that," she says, discussing the costs to her career. "I didn't think they would make my life a personal issue. I thought people would be more intelligent," she says. And, reflecting on the political atmosphere of the times, she asks, "What did it do? We didn't bring down any city, any government, like they were saying. We were just two people who wanted to be together and somehow, unfortunately, it lasted only 10 years. But everyone is happy now." Both have remarried; her fourth husband is a manager for Sabena Airlines.

This week Toure is also in town, and she says they have talked. "Even when I chicken out, I keep good relations, it's too much effort to stay nasty," she laughs. But she closes off any more personal talk. "I do not like to talk about my private life in the news. I always tried to avoid that. That's why most people don't know I am divorced from Stokely. People still call me, ask me, 'How is the brother?' and I say 'Okay' and leave it. Anything else is too Hollywood and I am hardly a Hollywood star. I don't have the glamor. Somehow there's a feeling that artists have to say everything and anything about themselves. I just believe some things are sacred," says Makeba.

Some people would argue that Makeba has stood for something more lasting than glamor, that she has symbolized artistic integrity and consistency. "I haven't changed because my world hasn't changed," she says. "I always have been branded a political singer but I sing about life. If it becomes political, that's because it's real."

Through the years, her songs have prodded her listeners. In "Khawuleza (Hurry Mamma Hurry)" she warns, "Hurry, mamma and hide/The police are on their way," and in "Baile Banahe (Gone Are My Children)" she laments, "Our sons have been sent to the mines/perhaps never to return."

But right now she refuses to discuss American politics. "When you are in somebody's house you have to behave as a guest. You cannot abuse your host," she says. But she finds the Reagan administration's openness to the Pretoria government "sad." Like all refugees, she would like to go home someday. South Africa stays with her like an unhealed wound. "One feels outrage because what is being done is outrageous," she says.