Access Exclusive: Inside Katy Perry's 'Cosmic' AMA Rehearsals

When Katy Perry takes the stage at Sunday's American Music Awards in Los Angeles, it's going to be truly an out-of-this-world experience.

Access Hollywood has exclusively learned that Katy will be performing an acoustic version of her song, "The One That Got Away."

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Not only will Katy provide the vocals, but she'll also be playing the guitar herself, a source has revealed to Access .

"She sounds fantastic," the source told Access after seeing Katy's AMA rehearsal. "[She is] showing off her talent as a musician."

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As for the stage, Katy will perform in a "cosmic" setting on a circular platform in the center of the stage, the source added. The set will be complete with laser effects and a giant screen behind her "filled with asteroids and stars."

Besides her performance, Katy is also up for three awards on Sunday, including Artist of the Year.

The 39th annual American Music Awards will be held on Sunday, Nov. 20 at the Nokia Theatre in Los Angeles. It will air live at 8 PM on ABC.

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