Moriarty keeps his gaze on Oswin, and permits himself a small smile at her expression.

(Mostly because he likes seeing her happy. Partly because the last person to enjoy his music so much was the Viceroy - although Moriarty could never be sure if it was the music or the act of playing that brought him so much pleasure - and it's good to have a memory to supplant those.)

Before long, he's moved on to Paganini's Caprice #8.