He hums and it's a warbling sound, too even and understated to be overtly cheerful, per se. The definitely-not-a shit-eating grin, on the other hand, probably gives him away.

Hold onto that. It's unclear what exactly he's responding to, but his hands clasp and lace for a moment before he untangles them to continue. If you were a romantic you wouldn't be you.

Though the sight would be something to behold...