Crosby Stills Nash & Young

"At this point, it's not about would we get together," he says. "Should we, is the important question."

Fillmore East performance arrived a little more than a month after their famous Woodstock appearance.

Defining folk rock is a paradoxical task, to say the least.

He wrote "I Watched It All Come Down" to express his regret they didn't do more together.

"His legacy will continue to live on through his legendary music," Crosby's wife said in a statement.

"Stephen [Stills] and Neil [Young] and I are great," Nash told 'CBS Sunday Morning.' "We talk often. We don't talk to David."

Trio brought Neil Young on board shortly after releasing their debut album.

On May 4, 1970, National Guardsmen squared off against anti-war demonstrators on the campus of Ohio’s Kent State University.