It's your laugh. More specifically when he makes you laugh, nothing else from any person or the beauty of nature can fill his heart with happiness and love. Everything about you to him is always perfect, so when you let out a good laugh and seem genuinely happy there is no way to describe how good he feels. The world will stop dead in its tracks; all that exists is you and him. He will likely try his best nearly all the time, mainly while you're in private, to get you to laugh.

The sound of your voice is also something that he loves. It's the sweetest thing to his ears and he can never get enough of it. He'll even ask you to read something for him now and then just to watch and hear you. Sometimes if you have been working a lot and don't see each other for a while he'll just ask you to tell him everything that happened while you were apart. If you're talking in another room he might stand outside the door and listen to every word you say. If you were to die it would be the sound of your voice that he would miss the most and would try and keep a hold of your voice for as long as possible.