OK. I got a big shock today. My 4 year old son, Wife and I are riding in the truck with the radio/CD playing as normal. My son is singing along (as he usually does) and he asks my Wife or me to sing with him. My wife starts to sing the song with him and when the song gets to the chorus my kid jumps up to the harmony part!!! And he did it every time the chorus came around. Now he's heard me do this to songs a thousand times (I regularly sing harmonies that are not even there because its good practice for the ear). Could he have actually caught on to what I've been doing? Anybody else with similar age kids have this (or something like it) happen? He is my only child so I don't know how common this might be at this age. And here I thought he was just going to be a bass player.