Taylor Swift has confirmed a folklore mystery! During her new Disney+ concert film, folklore: the long pond studio sessions, the 30-year-old singer revealed that William Bowery, the mystery songwriter credited on "Betty" and "Exile," is actually her boyfriend, Joe Alwyn.

"There's been a lot of discussion about William Bowery and his identity. He's not a real person," Swift tells collaborators Aaron Dessner and Jack Antonoff in the film. "... William Bowery is Joe, as we know. And Joe, Joe plays piano beautifully, and he's always just playing and making things up and kind of creating things."

The couple first teamed up for "Betty," a song for which, Swift revealed, Alwyn wrote the chorus.

"I just heard Joe singing the entire, fully formed chorus of 'Betty' from another room. And I just was like, 'Hello,'" Swift recalled. "It was a step that we would never have taken because why would we have ever written a song together? This was the first time we had a conversation where I came in and I was like, 'Hey, this could be really weird and we could hate this, so could we just, because we're in quarantine and there's nothing else going on, could we just try to see what it's like if we write this song together?'"

The partnership worked out well, with Alwyn inspiring the idea to tell the story of 'Betty' from a male perspective.

"He was singing the chorus of it and I thought it sounded really good from a man's voice, from a masculine perspective," Swift said. "I really liked that it seemed to be an apology... We decided to make it from a teenage boy's perspective, apologizing after he loses the love of his life because he's been foolish."

Next, Alwyn contributed to Swift's collaboration with Bon Iver on the song "Exile."

"'Exile' was crazy because Joe had written that entire piano part and he was singing the Bon Iver part... He was just singing it. And so, I was entranced and I asked if we could keep writing that one," she said. "It was pretty obvious that it should be a duet, 'cause he's got such a low voice and it sounded really good sung down there in that register."

Fans first suspected that Alwyn was Bowery before folklore even came out. The speculation started when Swift announced the surprise album and thanked collaborators Bon Iver, Dessner, Antonoff, and Bowery. 

Bowery was an unknown name to fans, and the only one of the collaborators who wasn't tagged in Swift's post. After no registered songwriters or producers could be found with that name, sleuthing fans dug deeper.

It was then that people remembered that, in the early days of Swift and Alwyn's romance, they were photographed outside the Bowery Hotel in New York City. Then it came to light that Alwyn is the great-grandson of English composer and musician William Alwyn. With those facts in hand, Swifties were convinced about Alwyn's secret identity.

folklore: the long pond studio sessions is available on Disney+ now.

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