Fans at Tootsie's in Nashville got a shock last weekend when Steven Tyler emerged from the crowd to join Keith Urban on stage. The country superstar was playing the honky tonk as part of a promotional tour for his new 'Fuse' album when he summoned the Aerosmith singer with the riff from 'La Grange' by ZZ Top.

“I’m going to attempt an experiment right now," Urban says in the video from Friday night. "I’m going to predict if we play this riff long enough, we might find a singer in the crowd who knows how to sing this song.”

“If you happen to be a bit of a badass blues legend singer, this might be your cue.”

Tyler begins by scatting over the famous riff before working the lyrics of 'Walk This Way over the blues jam. That all came after the former 'American Idol' judge told the current 'American Idol' judge to give Jennifer Lopez a gift for him. He then planted a kiss on Urban.

'Fuse' hit stores on Sept. 10.