Talk about fan appreciation!

When a fan asked to join Keith Urban on stage, the country singer, 42, did one better: He let him play!

At a free concert in a parking lot outside a Verizon Wireless store in Padadena, California, last month, Urban performed songs requested by some of the 1,000 fans in the audience.

Fan Corey Kramer's request?

He asked the singer to perform his hit, "Days Go By" -- with him.

Without hesitation, Urban invited Kramer onstage and the two strummed on their guitars -- Urban autographed Kramer's! -- and sang the song together. (Watch the clip above.)

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"Nice pickin' with you," Urban said after the performance.