so in Keith's rendition, the music actually sounds a lot like the album cut. so then he wrote this song on his own? and then Mick eventually did the vocals and they decided they needed another vocal over the top for emphasis? which eventually turned out totally making the song a smashing hit.
am i getting this right?
I don't know for sure. Keith worked a lot on his own, sometimes with Charlie. He is/was pretty good on the bass as well as the guitar. The version with him on vocals is the same basic arrangement as the final version but is not as well recorded. If you listen closely, there might be some Mick backing vocals tacked on. It sounds like a demo. It was only ever leaked on boots.
In the once lost and now found film,
Charlie is My Darling, we see the Stones on tour in Ireland in 1965. They are basically just a bunch of kids, and Keith is so very shy - has to turn his back on the audience at times, not comfortable with the camera at all. And of course, Mick is Mick. There are a few seconds of Mick and Keith in a hotel room working on a song that would end up on
Between the Buttons.
Working seems to be Keith shyly singing and playing for Mick what he has written and then Mick more or less saying something to the effect that he doesn't like this part so change it, Keith.
It also has Keith doing impromptu acoustic covers of some Beatles songs that he admires.
It's a pretty good film if you can find it somewhere.