Found the article on the background to the session.
It was posted on Martin Elliott's excellent 'Stones Sessions' facebook page on October 1st (thanks, Martin) :
LET'S GO STEADY AGAIN
A classic out-take featuring a duet between Keith Richards and Kristi Kimsey (Chris Kimsey's wife) on this 1959 James Alexander-penned Sam Cooke tune, which was the B-side to Only Sixteen. Neil Sedaka later covered it in 1963 and enjoyed a single chart entry with it.
On one occasion in Nassau, when Keith was working late, he called Kristi in the middle of the night and asked if she could pop down to the studio. Explaining that she might not give her best vocal performance she agreed to meet up the next day. She walked into the studio and listened to the backing track recorded the previous night, with Ron Wood on bass, guitar and saxophone. Then, with Keith, she took to the stage - much to husband Chris Kimsey's surprise - and improvised the duet, not even agreeing which lines they would sing. Kristi recalled that, for some reason, the control room was full of onlookers but together the cut was made. It is a splendid ballad full of soulful ramblings. There is an alternative mix with less guitar (* a - 2.51). Chris was very proud that she did such a fantastic performance on it. “She did really good! I mean, yeah, really really good! I mean, she had no time to learn the song. It was as if they had always sung together. It was quite special.” During the Covid ‘Lockdown’ of 2020/2021 Chris Kimsey and Kristi Kimsey went through their DAT tapes of Kristi’s solo recordings. They prepared a retrospective album of her songs from their stay at Long View Farm, Massachusetts in 1978 where they had been working with Frank Carillo on his album RINGS AROUND THE MOON. Chris was the producer and Kristi featured as a backing vocalist along with Yvonne Elliman. After dinner in the evenings Carillo’s band backed Kristi on her compositions. This mainly constituted her album released in September 2021 AS I LOOK BACK. Chris had the idea to contact Keith and he kindly agreed that her joint recording of Let’s Go Steady could also be included.
The recording is available for streaming and download from the usual sources. Further information:
https://undercover-music.compersonnel :
Keith - lead vocal, guitar, piano
Ronnie - guitar, bass, sax
Charlie - drums
Kristi Kimsey - lead vocal
Recorded at Compass Point Studios, Nassau, Bahamas, Jan-Feb 1979.