David Crosby and Graham Nash, two of the anti-Vietnam War era's most prolific singer-songwriters -- and core members of Crosby, Stills, Nash and Young -- team up once again to relive the magic, now as a duo. From "Long Time Gone" to "Teach Your Children" to "Our House," the concert is sure to turn into a sing-along. Monday, May 2, at 8 p.m. Music Center at Strathmore, 5301 Tuckerman Lane, North Bethesda. Tickets are $35 to $125. Call 301-581-5100 or visit strathmore.org.