It’s no surprise that an off-Broadway revival of August Wilson’s The Piano Lesson would be worth seeing. After all, the play won the 1990 Pulitzer Prize for Drama and is considered one of the best of Wilson’s masterful “Pittsburgh Cycle” set in each decade of the 20th century. But Ruben Santiago-Hudson’s production at Signature Theatre Company is a revelation in every way: perfectly cast, perfectly staged and perfectly acted by an ensemble at ease delivering Wilson’s poetic dialogue and in sync with one another. Tony winner Chuck Cooper mines the depths of the dandyish Wining Boy and offers delicious musical interludes. Roslyn Ruff, so good in Signature’s 2007 revival of Seven Guitars, makes Berniece a towering moral force. James A. Williams grounds the play as Doaker, and Eric Lenox Abrams is pure sweetness as Avery. Especially exciting is the casting of real-life brothers Brandon J. Dirden and Jason Dirden as Boy Willie (who is bound and determined to sell the carved piano steeped in family history) and his sweetly dim sidekick, Lymon. Dirden gives a star-making performance as Wilson’s problematic hero, and his confrontation scenes with Ruff are electric. Although Wilson’s plays (other than Fences) have never been long-running hits, Ruben Santiago-Hudson’s beautiful revival of The Piano Lesson deserves an immediate Broadway transfer and multiple Tony nominations. This is what a night at the theater is supposed to be.