The convergence of Crosby, Stills, Nash & Young has historically brought out some of the worst in each of those enormous talents, both personally and musically. But when separated from the pack, two of those guys—David Crosby and Graham Nash—actually make each other shine. Both men have strong songwriting skills and sweet, crystal voices, blending together gracefully and creating a breezy, high-altitude harmonic atmosphere. While they can veer toward the sappy on some of their more political and environmental songs, they are at their best when they turn inward, evoking an elegant melancholy and introspective regret, the kind that middle-aged men are much better at conveying than the youngsters Crosby and Nash were in their heyday. BRIAN J. BARR

Wed., March 30, 8 p.m., 2011