It's not a huge surprise to Taylor Swift concert-goers that the 'Mean' singer likes to invite famous friends on stage for guest appearances, especially in the big city hubs. But even the biggest fans don't know just who Swift will bring to the mic, and at her Speak Now show in Nashville on September 16, it was the legendary Ronnie Dunn.

"One of the greatest vocalists in country music, Mr. Ronnie Dunn is here ladies and gentlemen," Swift asked Bridgestone Arena, which erupted in screams. She and the Brooks and Dunn hitmaker seemed casual in front of the sold out crowd, seated comfortably on her vintage gold couch.

After a formal introduction, Swift took Mr. Dunn's arm and the pair waltzed to the front of the stage, where a pair of microphones were waiting. Without hesitation, and without a guitar, the iconic country performer led into an echoey version of his big 2011 hit, 'Bleed Red.' When the chorus rolled around, so did Swift's assistance, and the duo enticed the crowd to clap along as they sang together.

Taylor Swift's Speak Now world tour continues tonight, September 17, with another stop in her hometown of Nashville, Tenn. No word yet on who, if anyone, will make a guest appearance!

Watch Taylor Swift and Ronnie Dunn Perform 'Bleed Red'