Going through some scratched up old CDs, I found a copy of the Crosby, Stills and Nash release Carry On (Atlantic 7567804872, 2006). Entering some dates to trace Croz's whereabouts in the various periods in which he frequented the Garciaverse (most intensely, fall 1969-fall 1971 and again March-September 1975), I am reminded that Crosby, Stills, Nash and Young's "Ohio" was released as a single on June 4, 1970 [see also wiki].
Passing thought that Garcia could never have dropped a true protest song. On June 4, 1970, he played an amazing night of acoustic tunes (including two gospel numbers), country music on pedal steel guitar, and loud electric rock and blues.
Enjoy this incredible audience recording by Gerry Olsen (shnid-123798) that will put you into the comfy-as-home Fillmore West on a Thursday night. Yeah, "Darkness, Darkness", but sometimes it's better just to play.