"Sara" (Fleetwood Mac)

The entire Tusk album, Fleetwood Mac's 1979 follow up to the bajillion unit-selling Rumours (1977), is an interesting affair.  There's very little middle ground on the record (or maybe I should say "middle of the road"), and a definite concerted effort to avoid typical pop song structure.  
When you listen to Tusk, you don't go looking for radio-ready sing-along choruses à la "Don't Stop" or "Go Your Own Way," because they simply aren't there.  More or less, you have Lindsey Buckingham's jittery, coke-fueled forays into rockabilly-tinged New Wave sharing living space with Stevie Nicks and Christine McVie's watercolor balladry.  Sometimes the eclecticism works; other times it sounds like three different albums spun through a Cuisinart--particularly by the time you reach the end of disc two.
But the album is held together by pivotal moments like Nicks's "Sara."  
Like many of the other songs on the album, Nicks throws the "verse / chorus / verse" formula out the window on "Sara."  Instead, there's a loose web of verses and bridges, held together by her poetic lyrics and these otherworldly stacks of piano chords and acoustic guitar.  
(In fact, whereas everyone else on the web wants to dissect the hell out of her lyrics and figure out what/whom the song is about, I want to delve into the music and production instead.)  
The arrangement on this song is genius: there are Christine McVie's dueling pianos (both a little tinny and ever-so-slightly out of tune), split evenly between the speakers with Buckingham's copious guitar overdubs--which are in tune, also split between the two speakers.  The effect is that, one moment, chords are ricocheting off one another between your speakers and then they're melding together in the middle like a single instrument the next.  
Anchoring the whole thing is John McVie's steady, pulsing bass and Mick Fleetwood's unfaltering heartbeat rhythm--which he performs with brushes for God's sake!  
But my favorite part of all is the multi-tracked ooh backing vocals; they sneakily drift in like a fine mist, and then there are suddenly ten Stevies, Christines, and Lindseys, angelically hovering above the track.   I remember literally curling up next to the floor speakers of my parents' stereo when I was a kid and listening to those oohs and feeling like it was a warm blanket surrounding me.  It was (and is) one of those songs that I wished went on for hours and not mere minutes.