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Jack Antonoff is an American singer, songwriter, record producer, musician, and multi-instrumentalist. He has been a member of the bands Fun and Bleachers, and has worked on songwriting and record production with a variety of artists, including Taylor Swift. He has produced several of Swift's albums, including 1989, Reputation, and Lover. He has also written songs with Swift, including "Shake It Off" and "Blank Space."