When August Wilson writes plays he listens to the blues: He mines black American music to reveal on stage the history and philosophy of black America, which has largely been preserved and passed on via the oral tradition.

"When I discovered the blues something very important happened to me," says Wilson, in town recently to see his play, "Ma Rainey's Black Bottom," which has been extended at the Studio Theatre through Sunday.

"It was the first time that I recognized within black life something of value," he says. "It occurred to me that contained within this music was an entire people's cultural response to the world. And that if one was willing to listen . . . there was actually a system of values at work that was being expressed."

"Ma Rainey," which among other issues deals with the economic exploitation of black performers in the 1920s, is one in a series of plays Wilson is writing -- each set in a different decade of the 20th century, each exploring the most significant issue that blacks confronted in that decade. "So that if you put them all together you kind of get a historical overview of the black experience of America," says Wilson. "Although it is by no means complete."

Beginning with "Ma Rainey" in 1982, Wilson's last four plays -- including "Fences," which is scheduled to open on Broadway next March starring James Earl Jones, and "Joe Turner's Come and Gone," which is currently touring the country's regional theaters -- have originated at the Yale Repertory Theater.

"I think every regional theater in the country ought to . . . adopt a playwright for three years and commit to doing his work," says Wilson. "And I think by the third year you are going to have much better work from that playwright than you would otherwise.

"There's nothing like sitting down to write a play knowing that it's going to be produced," he adds. "I think you really write deeper in the sense that you want to reward the theater's faith in you."

Wilson, 41, was one of six children his mother raised by herself in a two-room cold-water flat in Pittsburgh. He is a self-educated man, having spent endless hours in public libraries after dropping out of school in the ninth grade. For many years as a young man he sustained himself by doing odd jobs. "The best I can say about Pittsburgh is that every day had to continually be negotiated."

While he was negotiating life in Pittsburgh, Wilson also was writing poetry, which remains "my first love," he says. "One of the things in American play-writing that I find lacking is the use of metaphor," says Wilson. "And of course in poetry this is what you deal with all the time, which is why my plays have these metaphorical qualities."

Given Wilson's 21-year career as a writer and the influence music has had on his work, it may come as a surprise that his artistic mentor is neither a poet, nor a playwright, nor a musician but a painter, Romare Bearden, whose art Wilson was introduced to when he moved to St. Paul in 1978.

"When I discovered Bearden's work, I saw in his canvases, in his collages, in his paintings, all the things I wanted to say," says Wilson. "There is a richness to them. They are just filled with vitality and brimming with life. So I thought if I can write like he paints, I would be satisfied. And I'm still trying to do that.

"I work off a quote from Romare Bearden," continues Wilson. "He said: 'I try to explore, in terms of the life I know best, those things which are common to all cultures.' And I thought, 'That's what art should do.' I mean, that's the best an artist can do. So I try to do that in my work -- to explore within the black experience and to uncover the commonalities of culture."

Wilson's next project is to write the book for a musical about Jelly Roll Morton, which will star Gregory Hines and is scheduled to open on Broadway next spring. The script is due Sept. 1, but Wilson hasn't started it.

"I have no idea what the story is yet," he says, adding that he plans to listen to Morton's recordings. "I'll find the story in the music."