He touches Joly's elbow at the reference to Musichetta. Yes: Musichetta's presence would make things entirely different.

"I don't know that very much need change. Er--that is--from how things have been here. That is--erm. I haven't exactly been cultivating the company of grisettes, wandering the streets at midnight, sleeping on Grantaire's floor, hunting up demoiselles at the ball; I'll grant you that a lack of grisettes, streets, and dance-halls might have something to do with it but, erm." He clears his throat. "I've had a sort of a notion of fidelity lately. Novel thought, I know, but..."