"It's a lullaby, yeah." He smiles, trying to reassure Sherlock that he's doing well. "That's good, that you remember it a little. It's nice. You used to play it sometimes." After he had particularly hellish dreams, actually. They didn't talk about it, but...well, it was there.

He hesitates, not sure if it's too soon. "We've...got your violin here now. If you ever want."