The Choir of Christ Church Cathedral in Dublin, on its first visit to Boston, fills Old South Church in the Back Bay with song. Old South is observing its 350th anniversary — but it’s a mere kid compared with the renowned Irish ensemble, which traces its roots to 1493. Celebrate Irish culture and sing along, starting with “Sing Joyfully” and ending with “The Blue Bird.” 7 p.m. Free; RSVP required. oldsouth.org
Acclaimed playwright Kirsten Greenidge ventures into Sleep No More territory with Greater Good. The audience roams the halls and classrooms of the Back Bay’s Commonwealth School, exploring the interactive story of a community grappling with the fallout of a mysterious incident at a parent council meeting. The Company One Theatre/American Repertory Theater production runs through August 17. From $25. americanrepertorytheater.org
A New (to You) Leaf
Plagued by unread beach reads? Haunted by the long-ago book group picks you haven’t even opened yet? Keep what sparks joy and tote some others to the Annual Brookline Booksmith Book Swap. Trade your old volumes for fellow bookworms’ castoffs in the basement from 6 to 9 p.m.; leftovers go to charity. Free (unless you count all that money you spent on books). brooklinebooksmith.com
Dozens of vendors from the Boston area and Latin America fill the stalls at the JP Flea Summer Market. Shop for jewelry, clothing, vintage merchandise, home goods, and more, and pause for a palm or tarot reading or a snack. The quarterly event, outdoors at the Eliot School of Fine and Applied Arts, runs from 10 a.m. to 4 p.m. both days. Free; $1 donation suggested. jpflea.com
One Small Step
Half a century has passed since Neil Armstrong and Buzz Aldrin “came in peace for all mankind.” Celebrate the 50th Anniversary of the Moon Landing at Acton’s Discovery Museum by building landing pods, blasting off with stomp rockets, taking a fitness test to see how high you can jump on the moon, and more. 11 a.m. to 2 p.m. Included in museum admission ($14.50, kids under 1 free), discoveryacton.orgShare your event news. Send information on Boston-area happenings at least four weeks in advance to email@example.com. Follow us on Twitter @BostonGlobeMag.