Some have joked that the only difference between Taylor Swift and Carly Simon is 45 years. Both songwriters are given to writing confessional break-up pop songs. Simon, 68, has been asked about the subject of 1972’s classic You’re So Vain since the song’s release, and she has resisted revealing the identity of her Lear Jet-lovin’ lover. And we are probably never, ever going to learn the true identity of the men behind Swift’s songs.

So the two just had to perform together at some point, didn’t they?

On Saturday, Swift, 23, brought Simon out as her Red Tour special guest to perform You’re So Vain together before 55,000 fans at the Gillette Stadium in Foxborough, Mass.

The resulting video has since gone viral.

“Once we get out there, and we have 55,000 people in sing-a-long it will be like karaoke night in the stadium,” Swift said backstage before the concert as she sat next to Simon, clad in dark sunglasses. “Every girl will be thinking of someone when we’re singing.”

After the frisky performance, the famously stage-shy Simon told The Miami Herald, “It was a total plus. I couldn’t have asked for a better evening. I was so tickled that Taylor so openly gave me a nod. Taylor, her mother and her father are as good as gold.” Simon also joked, “there was that soul connection between Taylor and me.”

Sure enough, in a promotional video sent by Swift’s publicists, the two confessors dished about dissing their men in song. Simon’s romances included Kris Kristofferson, Cat Stevens, Warren Beatty and, of course, ex-hubby James Taylor. Taylor’s exes include Jo e Jonas, John Mayer, Jake Gyllenhaal, Conor Kennedy and One Direction’s Harry Styles.

“When I heard You’re So Vain I thought, ‘This is the best song ever written.’ That is the most direct way anyone has ever addressed a breakup,” Swift said.

“It’s a song that sort of developed that style of mine and a lot of it was not knowing I was developing that style,” Simon said. “A lot of things happen by accident.”

The pair also shared another revelation. Swift now knows the identity of the man in the apricot scarf who walked into the party like he was walking onto a yacht.

“I’ve already told you and told you never to tell,” Simon said.

“But I do know now,” Swift teased.

— HOWARD COHEN