Quilapayun is not what it used to be, and to tell the truth, the members of this Chilean folk group couldn't be happier about that.

Not that the septet will have a radically altered sound when it appears tomorrow at Lisner Auditorium. Despite a wider repertoire and the addition of a few electronic instruments, Quilapayun still makes the same connections between traditional South American and contemporary western music.

Instead, the difference lies more in what the group is believed to be about. Back in 1965, when Quilapayun was formed, Chile was in the midst of a rediscovery of its own popular culture and in the beginnings of a social revolution that culminated in the Popular Unity government of Salvador Allende. The name of the group is the Auraucanian word for "bearded men." Quilapayun used Indian instruments, the Chilean folk repertoire and their own training in classical music to create an impressive body of songs about the struggle for social justice.

Quilapayun worked for three years with the renowned singer/poet Victor Jara and became phenomenally popular, not only in Chile but throughout Latin America. But after the coup that overthrew Allende's government in 1973, while the group was touring France, the members of Quilapayun became exiles and activists.

In the process, Quilapayun's purpose became somewhat misunderstood, argues member Rodolfo Brava. "After the military coup in Chile, people saw us as the symbol of the solidarity with Chile," he says, "in spite that we have always had a very deep artistic project, no? But the conditions of Chile, the conditions of Latin America, the conditions of our lives forced us to take that responsibility. We are proud of that. We did it, and we think it was well done.

"But time has already changed it . . . We would like to make people understand that we have a cultural project that is, in some part, connected with the nowadays reality. But it is an ambitious project, to participate in the most creative way in the construction of the Latin American culture."

Brava is referring to the New Song Movement, a sort of musical equivalent of the boom in Latin American fiction and painting.

"It's an expression of the last years in Latin America, an expression which tries to realize our own cultural values in the face of international cultural penetration of our countries," he says.

Brava sees the goals of the New Song Movement as threefold. As he puts it, the music should encompass "the cultural aspect of the defense of our own roots; the social and political context to participate in the hope, the utopias of this continent; but especially the creative ambition."

Obviously, part of the process depends upon the group's own output, as it continues to blend Chilean folk music with other, more westernized styles. After all, Brava insists, "in what we do, we have never been folk musicians. We have never done folk research, we have never wanted to be the repetition of the folk music as it was played before. Never. We have always taken the folk element only as a base to construct a new music.

"Well, the matter is, we are the sons of the sons of the sons of the Spaniards, European people in general, and also of the Indians, the black people and so on. We are a synthesis of many cultures. So what we do now is to continue the character of synthesis in our particular conditions."

Which is how Quilapayun's repertoire has come to include some rather unexpected titles. For instance, the Beatles' "Eleanor Rigby."

"It's an instrumental piece which we play with our folk instruments," Brava explains. "It's quite astonishing, but I think that all the music, in the deeper sense of this action, is to show that every popular music has a very deeply popular and universal content. That's why we play a Johann Sebastian Bach piece with our folk instruments, and also a song of the Beatles."

In all, Brava argues, the members of Quilapayun "have become more creative people, and what we want to show this time, in relation with what we showed before, is that we have changed. We have done new songs, we are crazier, we are not just political symbols. We are not just people agitating people to express their solidarity with Chile. We are defending our identity, our personality, and we feel nowadays stronger to create our own music, to express our own spirit with liberty, and to express our sense of humor and irony in music.

"We feel more free," he says.