Be a post whore!

[Clodfobble]

If you're sure it's the social/intimacy aspect, you might try puppets or toy action figures, pretending it's them singing to each other rather than you singing to him. Or he might respond better to a simple recording of you singing instead of sitting through it in person. I don't know what the Singing Cat is, but if it's a separate object that plays songs, that would serve the same effect.

But there is also the possibility that it is the actual sound of singing that bothers him, and he's just being as polite as he can about it when what he really wants to do is clamp his hands over his ears. Both of my kids absolutely couldn't stand to listen to people singing in person, although singing on TV or the radio or whatever was fine. Minifob is long past it now, and Minifobette has learned to accept her therapists and teachers singing, but anyone else even starting to hum is still going to be met with tears.