Claire de Lune is a classical piano piece composed and played by the musician Claude Debussy. Edward plays it in the movie I think. And in the book, he says that he likes Debussy. Jonathan Smith, on Highway to Heaven, also plays it in the episode "Keep Smiling" for his wife that he had when he was still human Jane. Who is oblivious that Jonathan is actually Arthur. Sorry that it got away from Twilight. Just needed to ad that extra bit of info.