From American Songwriter:
“Ruby Tuesday” defies expectations in a couple of ways. First of all, it’s a tender ballad courtesy of The Rolling Stones, so you might expect it to be a Mick Jagger creation. You’d be wrong though: As Mick told Jann Wenner in 1995: “It’s just a nice melody, really. And a lovely lyric. Neither of which I wrote, but I always enjoy singing it.”
Keith Richards actually did most of the work on the song, writing the lyrics after coming up with the music with the help of Brian Jones. That music is the second reason that “Ruby Tuesday” is such a surprise. Melodic ingenuity was supposed to be the domain of the Stones’ chief rival, The Beatles. Yet this song, which was a #1 hit here in the U.S. in 1967, has a downright gorgeous tune, aided by Jones lovely work on the recorder, proving that those things that we all had to play in grade school music could indeed have a purpose.
Richards claimed at different times that the lyrics were based on a groupie and on his mid-60’s girlfriend Linda Keith. Given his reputation, you can understand how Keith’s recollections might be fuzzy, but it’s impossible to deny he came up with a first-rate song. And he wisely left it in Jagger’s hands to deliver a moving vocal.