And having seen some YouTube of him doing The Pirate Fairy I just don't think singing is his forte. At Nuffiled he talked about how at RADA they focussed on making you improve your weakness (verse speaking, dancing, singing, etc). Someone asked him what his weakness was and he refused to say! I did wonder slightly cynically if that was because it was singing and he thought it would look bad because he had just finished filming ISTL.