Mike DelGuidice was 15 years old when he started playing Billy Joel’s music, but he never imagined he’d be playing alongside him one day. Growing up on the North Shore, DelGuidice spent a lot of time watching Joel’s Live from Long Island concert video and hanging out in the music room at Miller Place High School where he practiced the songs of Joel, Elton John and Paul McCartney. “The only training I had in singing was from my high school vocal teacher and she was great,” recalled DelGuidice, now 43. “That’s where I really learned about harmony and certain pitch techniques.”