(CNN) Taylor Swift called it her "worst case scenario," learning that her music catalog has been sold to a company owned by music manager Scooter Braun.
Claiming she's been bullied by Braun for years, Swift took to Tumblr on Sunday to explain how upset she is that her songs with Big Machine Label Group ended up with Braun, who manages artists such as Justin Bieber, Ariana Grande and the Zac Brown band.
Braun's Ithaca Holdings acquired Big Machine Label Group from founder Scott Borchetta as part of a $300 million deal, reports Billboard. Swift had been signed to the label from her 2006 self-titled debut album through 2017's "Reputation," before moving to Universal Music Group.
The sale prevents Swift from owning the first six albums in her catalog.
"For years I asked, pleaded for a chance to own my work. Instead I was given an opportunity to sign back up to Big Machine Records and 'earn' one album back at a time, one for every new one I turned in," Swift explained.
"I had to make the excruciating choice to leave behind my past," Swift continued. "Music I wrote on my bedroom floor and videos I dreamed up and paid for from the money I earned playing in bars, then clubs, then arenas, then stadiums."
Swift said she learned Braun was the buyer when the deal was made public.
"I learned about Scooter Braun's purchase of my masters as it was announced to the world," Swift wrote. "Scooter has stripped me of my life's work, that I wasn't given an opportunity to buy. Essentially, my musical legacy is about to lie in the hands of someone who tried to dismantle it."
CNN has reached out to Braun for comment.
"This is my worst case scenario," Swift wrote. "This is what happens when you sign a deal at 15 to someone for whom the term 'loyalty' is clearly just a contractual concept. And when that man says 'Music has value,' he means its value is beholden to men who had no part in creating it."
Swift signed off on a positive note, writing: "Thankfully, I am now signed to a label that believes I should own anything I create. Thankfully, I left my past in Scott's hands and not my future. And hopefully, young artists or kids with musical dreams will read this and learn about how to better protect themselves in a negotiation. You deserve to own the art you make."
Then she plugged her new album.
"I will always be proud of my past work. But for a healthier option, 'Lover' will be out August 23."
Signed: "Sad and grossed out, (broken heart emoji), Taylor."