Paul didn't really expect the singing to stop, didn't really expect an answer, but he narrows his eyes further (watch it, Paul, you're gonna just close them in a second if you keep that up) at the dig, as he perceives it, about the kissing.

The next line, though, makes his eyes widen right back up.

There's a notepad by a (non-functioning) telephone on the counter. Paul starts hastily scrawling down the lines of the song. Fortunately his memory's plenty good enough to fill in the lines already sung.