"The Only Living Boy in New York" (Simon & Garfunkel)

It's early 1969.  Art Garfunkel is in Mexico, trying his hand at acting in a film adaptation of Joseph Heller's Catch-22.  Filming is taking months longer than anticipated, and Paul Simon is back in New York City, trying to write new music for their upcoming album without his best friend to bounce ideas off of...
In Jennifer Lebeau's 2011 documentary The Harmony Game, which explores the making of the album Bridge Over Troubled Water (1970), Simon discusses the gestation of "The Only Living Boy in New York," noting that the "Tom" in the lyrics is actually Garfunkel (their stage names having been "Tom & Jerry" when they were teenagers, just starting out).  
In short, the lyrics are Simon wishing Garfunkel well on his acting debut (I know your part'll go fine), while also feeling abandoned, isolated, and slighted by a lack of communication (I can gather all the news I need on the weather report).  But, ultimately, it's a painful acknowledgment that they were drifting apart (Half of the time we're gone, and we don't know where / And we don't know where), both as friends and creative collaborators.
Despite the song being a virtual farewell to Garfunkel, it's also one of their warmest vocal collaborations on tape.  Their multi-tracked, sanctuary-echo aaahhh harmonies throughout are angelically uplifting and heartbreaking at the same time.
And then there's lauded session musician Joe Osborn's bassline--a living, breathing thing that glides and plucks at all the right moments.  It's one of the key elements, along with Hal Blaine's strategic bursts of percussion, that give the song an almost Pet Sounds quality (which, incidentally, Blaine appeared on).