John Mayer and Taylor Swift performed their duet song "Half of My Heart" years ago at the Z100 Jingle Ball, and after they broke up, both of them ignored its existence.
Up until Wednesday night when Mayer performed the song in Detroit's Little Ceasar's Arena during his solo acoustic tour.
According to Billboard, despite performing the song solo, the artist did not have to sing Swift's part of the song because his fans were gracious enough to provide the accompanying vocals.
Mayer has not performed "Half of My Heart" in 14 years, and given his nasty breakup with Swift was presumed to be, no one expected him to ever perform it ever again.
A fan tweeted about the "Gravity" singer's performance: "John Mayer played my favorite song of his last night for the first time in years.I cried. This song means so much to me."
"The week has been s**t. The month has been trash. This morning was full of arguments. I did not sleep. I feel entirely alone. But then, John Mayer plays Half of my Heart at last night's show, and it all went away in an instant," another added.
'Dear John'
The reason why Mayer and Swift pretend like their "Half of My Heart" duet performance never existed is mostly because of how nasty their breakup had been.
While there isn't much information about it, some fans pointed to Swift's 2010 song "Dear John" as a basis for how their relationship might have ended.
A line from the song goes: "Don't you think 19 is too young / To be played by your dark twisted games, when I loved you so?"
Swift was 19 when she dated the "Your Body Is a Wonderland" singer, who was 32 at the time.
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Shots Fired
He blasted her for writing a song about him and trashed her songwriting abilities in an interview with Rolling Stone in 2012.
"It made me feel terrible ... I didn't deserve it," he said. "I'm pretty good at taking accountability now, and I never did anything to deserve that. It was a really lousy thing for her to do."
"I think it's kind of cheap songwriting [...] I think it's abusing your talent to rub your hands together and go, 'Wait till he gets a load of this!'"
While their relationship has been over for over a decade, fans speculate that a song off Swift's recently released album titled "Would've, Could've, Should've" is about Mayer.
According to reports, "Half of My Heart" has not been performed in years, however, it has been well-received and even earned a Platinum certification from the RIAA.
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