Taylor Swift has been keeping company with some of hip-hop and R&B’s biggest stars on her “Speak Now” tour. One of her surprise guests, Usher, is praising the country crooner for her hip-hop sensibility.

Ursh performed his smash “Yeah! with T. Swift at Philips Arena in Atlanta earlier this month and was impressed when she tackled Ludacris’ verse and busted a few moves.

“For real, you guys don’t even understand. Taylor, yo, she’s crunk for real,” the R&B singer told Yahoo! Music. “In Atlanta, she came out. She did her thing. I didn’t know she and hip-hop swag like that. She came out and they enjoyed it. Then, the finale, my kids came on stage.”

Usher was enjoying a day off with his sons when he got the call to perform. “It started off as a simple day in the park with the kids,” he said. “We have minivan adventures. Taylor hits me, and says, ‘Yo Ush, I’m in town. I’d really love if you could come out and do ‘Yeah!’ with me.’ I’m like, ‘Well, we haven’t had any rehearsals.’ [She said], ‘No, no. The band’s got it. You just show up.'”

His oldest son Usher V. wanted to join his father on stage. “My son [was] looking at the stage saying, ‘Daddy, I want to go on stage.’ I’m like, ‘Son this is not Daddy’s show. It’s Taylor’s show.'”

In addition to Usher, Swift has performed “Super Bass” with Nicki Minaj, “Live Your Life” with T.I., and most recently “Airplanes” with B.o.B.