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.