Taylor Swift & Carly Simon Duet to 'You're So Vain': Watch

For Taylor Swift, breakups aren't always a bad thing. In fact, they usually result in a hit single and another platinum plaque to add to her collection.

And she's not alone. Pop music has had a long love affair with the kiss-off song, and some 40 years before Swift delivered the sugary delicacy "I Knew You Were Trouble," singer-songwriter and 70s icon Carly Simon, was doing the same with her signature single, 1972's "You're So Vain."

Combining the power of two jilted ex-girlfriends, Swift surprised audiences at her July 27 Red Tour stop at Foxborough, Mass., not far from Martha's Vineyard, where Simon has long called home.

Like Swift's "Dear John," "Last Kiss" and "We Are Never Ever Getting Back Together," the unknown person in Simon's hit was the subject of much speculation when the song shot up the charts. But in this performance, the two seem to be singing past flames everywhere.

Watch the duo's dazzling performance below: