Although it doesn’t mean to, this three-disc history-of-CSN box chronicles the rise and collapse of the hippie nation as embodied by David Crosby. In the early-years doc Long Time Comin’, the eloquent, baby-faced Crosby is the archetypal long-haired idealist (and hedonist). In the often creaky 1982 concert film, Daylight Again, taped in the midst of his drug addiction, he’s a waxy, expressionless zombie. The Acoustic Concert, from 1991, is surprisingly better: The harmonies and camera work are country-stream-clear, and post-rehab, Crosby’s twinkle (if not his leanness) is back. Of the three, Comin’ is the find: CSNY’s performance of ”You Don’t Have to Cry” on The Tom Jones Show, unseen Woodstock clips, and Hollies and Buffalo Springfield footage. Even better: an astounding bit of an irate Stills screaming at Crosby during an early clash. Anyone who behaved brashly and stupidly in his or her youth (and beyond — check out Nash’s ’80s mullet) will relate.