Yeah, it's remarkable that such a recording could even get released as it clearly fits in no category. Just goes to show what a unique time period that was – when rock and roll became "rock," and was in its full flowering – truly a modern renaissance for popular music. Coming from Van Morrison, Astral Weeks had to have been aimed at the rock/pop market but how did Warner Bros. even attempt to market it, or even describe it? Chamber rock-jazz? It has all the intimacy of chamber music, the inventiveness and spontaneity of jazz, the spirituality of gospel/soul, and the lyricism and magic of rock and roll. Just a perfect storm of a brilliant singer-songwriter following his muse, and consummate musicians to interpret them.
Not rock and hardly a song, but Joni Mitchell’s “Smokin’ (Empty, Try Another)” on Dog Eat Dog features a cigarette machine!
Oboe: surely that's one in Wishful Thinking by China Crisis? Harpsichord: Different Drum by the Stone Poneys? Less well-known but also excellent is If You Ever Need Me by Margaret Mandolph Jew's Harp: Mockingbird by Inez Foxx (also Lady Loves by Barclay James Harvest as I recall) French horn: fairly widespread actually, but Love Me Warm and Tender by Paul Anka springs to mind Banjo: Up on the Hill by Mark Burgess! Also Don't Bury Me Yet by the Raw Herbs
Let’s not forget Sam Spoons, of the Bonzo Dog Band. And speaking of the Bonzo, almost every track they did had weird instruments on it. How bout Roy Rogers on Trigger, for example?
Organ isn't unusual in rock, but a giant church organ like the one Rick Wakeman played on Yes' "Parallels" is:
Third or fourth mention of a oboe so far. Nonetheless, the most usual unusual instrument seems to be the harpsichord with lots of mentions.
You can't miss the glockenspiel in Bruce Springsteen's "Born To Run," as well as a few other songs on that LP.
If I recall correctly, Lindsey Buckingham recorded a couple of drum fills on "Second Hand News" with a chair and/or a Kleenex box.
Inca Roads, Marimba (or vibraphone, depending on version) Integral to the song. great solo. Or this version https://www.youtube.com/watch?v=nHWLcS-24A8 Thank you, honey.
Euphonium: in this bridge - Ivar Avenue Reunion, Charlotte Brown: (Edited to change the YouTube link, since the euphonium was barely audible in the first one)
Apparently Rick played the organ parts on “Parallels” and Awaken on a real church organ in the Swiss town of Vevey. They were phoned in to the recording studio in Lausanne or Montreux or wherever Yes was recording the album.
So. Many. Extreme metal bands. Seriously. There are an almost absurd number of atmospheric black metal and doom metal bands that make regular use of cello (Agalloch and Wolves in the Throne Room come readily to mind). Austin Lunn (Panopticon) made extensive use of banjo on his album Kentucky. Dead to a Dying World has a full-time violinist, and SubRosa had two of them. There undoubtedly are many other examples.
this is a song maybe you have ever heard ... Led Zeppelin - Stairway To Heaven Instruments: Recorders
Under My Thumb, no contest. Although it is, on the other hand, a stupid bit of misogynistic boomer crap.