Whether working as a trio, or with their longtime friend Neil Young as a quartet, David Crosby, Stephen Stills and Graham Nash helped bridge the ‘60s and ‘70s with their tight harmonies and songs about peace, love and other idealistic hippie pursuits. The group formed after the singer-songwriters parted ways with their former bands: Crosby was in the Byrds, Stills was in Buffalo Springfield and Nash was in the Hollies. Their self-titled debut was an immediate hit in 1969, with songs like ‘Suite: Judy Blue Eyes’ featuring a mix of gently rocking melodies and the three voices blending in heavenly harmony. The next year, Stills’ former Buffalo Springfield bandmate Young joined them for ‘Déjà Vu,’ which was followed a few months later by the single ‘Ohio,’ Young’s bitter response to the National Guard’s killing of four students at Kent State University in May 1970. Since then, the members have gotten together in various forms to record and tour.