This article, on the reissuing of CSN&Y's Deja Vu" LP 50 years later, contains some fascinating nuggets I never knew. Among them: who the group considered recruiting into the trio before Neil Young and why they ultimately chose him. 

"Prior to Young's crucial arrival, musicians such as John Sebastian, Steve Winwood and Paul Butterfield Blues Band keyboardist Mark Naftalin were being considered for the fourth spot in the band..."

“David and Stephen were having dinner with [Atlantic Records head] Ahmet Ertegun in Manhattan. And during the dinner, Ahmet looked at Stephen and said, I know who you should get, man. And Steven looked at him and he said, ‘Who?’ And Ahmet said, ‘You gotta get Neil back.’ Steven said, ‘Are you kidding? I just did two years of craziness with this guy [in Buffalo Springfield]. He's in the band, he's out of the band, we're doing The Ed Sullivan Show, we're not doing The Ed Sullivan Show. This is crazy. Are you sure?’ He said, ‘Yeah, you gotta get Neil.’”

But there's more, including a demo of a very different sounding "Teach Your Children" and the huge name that came in to save the song, and another never released excerpt of "Our House," featuring Graham Nash and Joni Mitchell. 

Well worth a read and a listen if you were a fan of either the album or the group. 

"Crosby, Stills, Nash & Young Mark 50 Years Of ‘Déjà Vu’ With New Retrospective Set"