College freshman Michael Pollack achieved YouTube virality when Billy Joel let Pollack accompany him on piano during a campus Q&A. Pollack's "New York State of Mind" chops evolved into a serious career as a collaborative songwriter who has added melodic color and spark to pop sizzlers by Charli XCX, Kelly Clarkson, and Lauv, as well as the down-home urban romance of Dierks Bentley's "My Religion."