Holmes rests his chin on the violin like a lover's shoulder. His grin nearly knocks it out of place, but he shoves it back. Watson's struggling to keep up with the quick tempo, but Holmes is delighted with his newfound pianist. When Holmes's playing makes the doctor doubt his soundness of mind, Watson must cry out, half laughing, "Stop! Stop it, Holmes!"
Holmes does, with great peals of hilarity. "All right, steady on, old man. For pity's sake, why did you never tell me you played the piano before?"
"I feel as though I never did play the piano before."