Paul McCartney had said it was "a sort of magic" playing music with Ringo Starr for their first post-Beatles collaboration.
The musical pair worked together on the song Beautiful Night, which was part of McCartney's 1997 Flaming Pie album, which is being re-released this month.
McCartney is also releasing a new version of the Beautiful Night music video, as well as a Beautiful Night EP.
He said: "I'd been saying to Ringo for years that it'd be great to do something because we'd never really done that much work together outside The Beatles.
"One night Jeff (Lynne) suggested, "Why don't you get Ringo in?" and I said, "OK." It just sort of happened.
"I had this song Beautiful Night which I'd written quite a few years ago. I'd always liked it but I felt I didn't quite have the right version of it.
"So I got this song out for when Ringo was coming in, and right away it was like the old days. I realised we hadn't done this for so long, but it was really comfortable and it was still there.
"So we did Beautiful Night and we tagged on a fast bit on the end which wasn't there before. And as we were coming away out of the studio into the control room, Ringo's doing like an impression of a doorman... 'all right then, on your way...', if you listen closely you can hear we left that in.
"In 2019 when I finished touring in Los Angeles, Ringo got up on stage and we were doing Helter Skelter together. And he's drumming away and I'm singing facing front because I was on the mic.
"But when I wasn't on the mic, in the solo breaks and stuff, I really made a point of turning round and watching this guy drum.
"And I'm thinking, my God, you know the memories across this 10-yard gap here, him on the drums and me on the bass, the lifetime that's going on here.
"So, you know, it's a sort of magic. And he and I these days get quite emotional about it, because we should. We ought to. It's a bloody emotional thing, the years. If nothing else."
Flaming Pie will be re-released as part of the Paul McCartney Archive Collection on July 31.
