If you need proof that T-Pain can actually sing without auto-tune - I've been assuming he couldn't all this time, honestly - watch him perform the National Anthem at Monday's Dodgers/Giants game at Dodgers Stadium.
"The Star Spangled Banner" is known to be a difficult song, but he basically nails it, and puts a lot of emotion into it, too. I got chills a few times. Fair play to T-Pain.
Here's a quick reminder of what he usually sounds like, in his new single "Make That Shit Work."