TWO SISTERS AND A PIANO | Nilo Cruz's poetic but ultimately unsatisfying play is steeped in longing: for an active life, for a husband, for revolutionary change. Writer Maria Celia and pianist Sofia are sisters living under house arrest in 1991 Cuba. It was Maria Celia's work on perestroika that forced their imprisonment; Sofia's playing keeps them entertained during the long, lonely days and nights. They're visited by Lieutenant Portuondo (Sammy A. Publes), at first a threat and later a symbol of all the freedoms the sisters no longer have. Charin Alvarez is too remote as the strong, idealistic writer--her final transformation is unconvincing, though part of the problem is the way the playwright breezes over the climax. But when Sandra Delgado's wild restlessness bleeds into despair, the production finally finds its emotional heart. Through 10/24: Wed 7:30 PM, Fri 8 PM, Sat 5 and 8:30 PM, Sun 3 PM. Wed 10/6, 2 and 7:30 PM. Sun 10/17, 3 and 7 PM. Thu 10/21, 7:30 PM. Apple Tree Theatre, 595 Elm Pl., Highland Park, 847-432-4335. $33-$38.