Dierks Bentley held his sixth annual Miles For Music celebrity motorcyle ride and concert in Nashville recently, and fans got a surprise when Lady Antebellum's Charles Kelley hopped onstage to join Bentley during his headlining set. The pair traded vocals on 'How Am I Doin'' before Kelley sang solo on 'Long Trip Alone.'

The annual event raises money for the Monroe Carell Jr. Children's Hospital at Vanderbilt in Nashville. In total the singer has raised over $2 million for Children's Miracle Network hospitals. The sta- studded lineup for this year's ride and concert included Kelley, Colt Ford, the Eli Young Band and Josh Thompson.

Artists donate their time, which makes for a loose atmosphere at these events. Collaborations are common, and Kelley certainly didn't look as if he was forced into swaggering onto the stage. He chose to sing Bentley's 'Long Trip Alone,' delivering a soulful rendition of the 2006 hit. Both men wore jeans and a baseball cap, a perfect outfit for the long motorcycle ride that proceeded the concert.

Bentley's official website reports that the 2011 Miles For Music event raised over $205,000.

Watch Charles Kelley and Dierks Bentley Perform 'How Am I Doin''