“The pure hormonal vitality” of the Shakespeare in the Parkproduction of “Hair,” writes Ben Brantley, “is enough to make it the pick-me-up event of New York’s dog days this year.” With choreography by Karole Armitage, it “registers as an eloquent requiem not only for the idealism of one generation but also for the evanescence of youth itself,” he writes. And when cast members invite the audience to dance with them onstage, “you can be forgiven for wishing you might never come down from that buzz of good will.”

“Let the Sunshine In, and the Shadows,” by Ben Brantley