D.Gray-man Vol. 14 (manga)

Song of the Ark

Cross Marian is about to finish off Tyki Mikk when the Millennium Earl barges in, spreading chaos and destruction in every direction! The Earl's plan to build a new Ark using data downloads from the old one seems unstoppable, until Allen encounters a strange apparition that tells him to play the piano. Allen would be more than happy to oblige, but there's one slight problem--he never learned how!