"Suite: Judy Blue Eyes" (Crosby, Stills & Nash)

As its title implies, "Suite: Judy Blue Eyes" from Crosby, Stills & Nash's 1969 debut album is a suite—a set of short, connected songs built around a common theme.  In this case, it was multi-instrumentalist and ex-Buffalo Springfield guitarist Stephen Stills writing about his then-girlfriend, folksinger Judy Collins, and the disintegration of their relationship.
In an August 2010 Sound on Sound article, Bill Halverson, the recording engineer on the session for "Suite: Judy Blue Eyes," recounts that Stills had the entire suite completely worked out before tape even rolled.
“It still gives me goosebumps when I listen to that recording, aware that he blew through seven-and-a-half minutes with all the time changes, all the pauses, all the everything, in just one take.  No edits, no nothing.”
(So the acoustic guitar and the main vocal you hear in the left channel throughout are the result of a single, uninterrupted take.  Pretty amazing.)
After Stills cut the initial track, the trio (also comprised of ex-Byrd David Crosby and ex-Hollie Graham Nash) overdubbed those incomparable CSN backing vocals.  There's nothing else on tape quite like the hair-raising vocal blend on the middle what have you got to lose? section.
And who couldn't love that Latin-flavored coda with those doo-doo-doo-doo-da-doo vocals that close the song?  As Stills told Debbie Elliott of NPR's All Things Considered in December 2012, the end section was a total afterthought, crafted in the studio.  Stills intended it as a lyrical and stylistic break from the rest of the suite to end it on an upbeat note, even going so far as to sing the lyrics in inscrutable broken Spanish.  (Basically, he's singing that he misses the beauty of Cuba and wishes he could visit again but, unfortunately, he can't.)  
Although Stills claims the coda is a non sequitur to the rest of the song, I think it's an extended metaphor about missing the early part of his relationship with Collins but realizing they could never go back again.
It's just an intelligent, epic song from an inordinately talented bunch of musicians who often exuded greatness when they weren't letting egos and chemicals get in the way.