REGULAR SINGING This is the fourth and final installment of Richard Nelson’s Apple Family plays, and it’s a beauty, a kind of collective meditation on death, memory, history, and the consolations of family. The production features the first-rate actors who appeared in the previous three plays, meshing as smoothly as a well-honed chorus, and is directed by Weylin Symes, who was also at the helm for “That Hopey Changey Thing,’’ “Sweet and Sad,’’ and “Sorry.’’ Through Sept. 25. New Repertory Theatre in association with Stoneham Theatre at Charles Mosesian Theater, Arsenal Center for the Arts, Watertown. 617-923-8487, www.newrep.org

MARJORIE PRIME Jordan Harrison’s drama is set in the near future, when technology enables 85-year-old Marjorie to sustain memories of her past with the help of a “Prime’’ that is an exact replica of her late husband as he was six decades earlier. Featuring Sarah deLima as Marjorie. Cast also includes Barlow Adamson, Lee Mikeska Gardner, and Alejandro Simoes. Directed by M. Bevin O’Gara. Through Oct. 9. Nora Theatre Company. A Catalyst Collaborative@MIT Production. At Central Square Theater, Cambridge. 617-576-9278, ext. 1, www.centralsquaretheater.org

SUNDAY IN THE PARK WITH GEORGE Peter DuBois directs the Pulitzer-winning musical by Stephen Sondheim (music and lyrics) and James Lapine (book) about art, artists, and obsession. Featuring Adam Chanler-Berat and Jenni Barber. Through Oct. 16. Huntington Theatre Company. At BU Theatre, Boston. 617-266-0800, www.huntington theatre.orgDON AUCOIN

Don Aucoin can be reached at aucoin@globe.com.