Legendary guitarist Carlos Santana is being treated for an unknown issue after collapsing on stage Tuesday night. Santana was performing at Pine Knob Music Theatre in Clarkston, Michigan when he fell about an hour into his set. Medical personnel tended to the musician on stage before transporting him to a hospital. A concertgoer says the crowd was asked to pray for him. The 74-year-old is a ten-time Grammy winner.