Kelly Clarkson -- This Fan's Got Pipes ... Get On 'The Voice' Yo!!! (VIDEO)

Kelly Clarkson clearly has closed the book on "American Idol" ... her go-to is now "The Voice."

We got Kelly in NYC where a hopeful soul busted out in song for the OG 'Idol' -- her song, of course -- and Kelly seemed impressed.

Check out the clip -- he might have a future with an assist from Blake Shelton and friends.