Swift's rep, Tree Paine, tells PerezHilton.com:
Wow. Wow. Wow.
Kanye is straight-up INSANE!!!!!
The Blow singer took the stage for the first time since leaving rehab at Petty Fest, a celebration of the music of Tom Petty! And she sounded so strong!
And natural! No autotune here!
Of course, she's performing the classic Free Fallin', so everyone is singing along! And it never hurts to have a whole audience of backup singers!
[Image via AP Images.]