Today's Piano Puzzler

This week's game features a contestant who is a celebrity of sorts, at least in the classical world.  Cameron Carpenter is the first organist to ever get a Grammy nomination for solo performance.  He clearly knows his classical music, because what's odd here is that he gets the composer style immediately, but is stumped on the popular song being hidden.  What's odd about that is I had found the song brain-dead easy, but couldn't figure the composer.  (As it happens, my stab in the dark was going to be his initial guess until he heard more of the piece and then changed his mind.  I had no particular reason on which to base that stab, but I couldn't think of who else fit.)