The presidential primary campaign is playing out across Pennsylvania, but if you can get your head off Page One and into the theater for a few minutes, I'll give you another sort of candidate, for Trouper of the Season, and she's a sure winner: Kala Moses Baxter. With only one day of rehearsal, the Philadelphia actress has scored an eleventh-hour save.

When the Arden Theatre Company's production of August Wilson's 1989 play The Piano Lesson, already an American classic, parted ways artistically with the actress preparing to play the no-nonsense character Berniece, director Walter Dallas and the cast were at the tail end of rehearsals and about to begin a week of preview performances leading up to Wednesday's opening night.

The Arden's artistic director, Terrence J. Nolen, phoned Baxter, who has appeared on Arden's stage before. Could she take over? The deal was cut, she swooped in, and, as it turns out, Nolen couldn't have made a smarter call.

On opening night, Baxter's performance was compelling and sure-footed. She fit easily into the production - which is saying something, given that Dallas' direction is exacting and the entire cast is superb.

You can't have a Piano Lesson without a strong Berniece; the woman owns the piano in question, and she's not parting with it nohow, even though her brother has a claim on half of it, which he wants to sell to buy a particular piece of land.

This is not just any piano, sitting in Berniece's Pittsburgh living room: It's been in the family for generations. Ancestors of Berniece and her brother, Boy Willie, were traded as slaves for it, another family member carved it into a unique instrument. Still another was killed retrieving it for the family.

And this is not just any farmland that Boy Willie (a muscular standout performance by Kes Khemnu) wants to buy; it's Mississippi land where their family once worked in slavery.

The play, set in the '30s, is part of the acclaimed 10-play cycle by Wilson, who died in 2005, in which he explored the African American experience over each decade of the last century. Like much of his work, this play pits the past against the future, as characters weave stories about themselves and their backgrounds into the basic, tense plot.

Dallas stages The Piano Lesson expansively, on Donald Eastman's high-ceilinged living room/kitchen set; the actors have room to move constantly as the argument over the fate of the piano intensifies.

The other leading cast members - Julian Rozzell Jr., Yaegel T. Welch, Brian Anthony Wilson and Harum Ulmer Jr. - offer textbook examples of how to bring characters off the page and build them on the stage. Even Katrina Yvette Cooper seems built into a minor role, and sweet Chioma Dunkley is pure innocence, a little girl amid the grown-up chaos.

There's no getting around the play's puffy second act; it's repetitive and at points seems endless. But it leads to a conclusion that is one of modern theater's great spiritual denouements, performed here fantastically. Which is entirely fitting.

The Piano Lesson

Through April 6 at Arden Theatre, 40 N. Second St. Tickets: $29-$45. Information: 215-922-1122 or www.ardentheatre.org.