Graham Nash played a pivotal part in at least two of the major musical movements of the classic rock era. He started his professional career as a member of the Hollies, a pioneering British Invasion group who defined a specific segment of '60s harmony-laden guitar pop. Once he left the band, he joined forces with Stephen Stills of Buffalo Springfield and David Crosby of the Byrds to form the supergroup Crosby, Stills & Nash, a trio that helped usher in the transition from hippie folk-rock to the reflective singer/songwriters of the '70s.