After having played the entire Friends album by the Beach Boys, it seemed natural that playing the whole Pet Sounds should be a priority. "Friends on Friends" (Matt Ouimet, Phil Bova, and myself) is a trio that covers Beach Boys songs instrumentally. While removing vocals from the Beach Boys songs sounds like it would diminish them, it really just showcases how strong the songwriting was.
"Don' Talk (Put Your Head on My Shoulder)" was the first song I learned off Pet Sounds- it's also the only song without backing vocals and none of the touring Beach Boys on it. As far as Brian Wilson introspection goes, this is a masterpiece. I'm also fond of "Busy Doin' Nothing" but that's not really as accessible to most people. Carmen McRae even did a version of "Don't Talk" on her somewhat badly received album For Once In My Life.
The verse is not exactly your typical pop ballad chord progression or structure. In it's 15 bars it starts as a traditional jazzy two-per-bar kind of ballad motion, albeit with a bass line often not on the root driving it. It balances that with a kind of ii-V vamp (the chorus) starting in the 6th bar, but it smoothly changes key in bar 11, somehow sliding back home again into the original key. Here there is a whole other set of theory problems, as the key is F# Major/Eb minor, two relative keys that enharmonically make for some ugly spellings if you were to stick to exclusively flats or sharps (Cbmin near the end or A#7 and D#min near the top). One specific chord fascinates me in that I wrote it two completely different ways in the same verse. Ebmin/Db and F#6/C#. The first feels like a resolution from the Bb7 and has a passing bass note, while the second has the kind of planted root sound not uncommon in Messiaen's music (often referred to as his love chord or theme).
Here is a version of Friends on Friends on Don't Talk.