When I was single, I usually had music playing from some source of other. I didn't own a TV at the time, so radio and recorded music was it. This tailed off once there were two of us, because other things occupied the time. When there was a small child around, music-related stuff tended to be aimed at the younger age bracket, although it was also a good excuse to play some Mozart.
More recently, I've been playing stuff and asking C what he thinks of it. He seems to enjoy punk and rock music, which is good because that seems to be what we've got a lot of. I have a bunch of classical stuff as well, but I need to organise a project to put that onto the computer from CD so we can listen to it more conveniently. Longer-term, encouraging C to listen to more music is going to be good. He's being taught piano and recorder and can read music, so there's a start to it. At some point I set up my old copy of Cakewalk on his computer and connected it to the Yamaha keyboard. He had some fun writing his own music, and seems to have an ability for it that should be encouraged. I did ask him how he did it and he showed me how he would try different notes until he found the one that sounded 'right'. He shows every indication of being much better at it than I ever was.
Today I decided to answer one of his questions (what's opera?) by playing Carmen. He stuck around for the first CD, but has now vanished off to play. Later, I'll go and ask him a bit about it and see what he thought. I always disliked opera until I got to see Carmen on TV, although I've since realised that what's bad about opera is the excessive vibrato of voices that makes them sound like cats in heat. Not all opera singers are like that, so it's very much a case of choose performances carefully.
It occurred to me that C is probably a bit young to understand the nuances of the story, but it's the only complete opera in the house. The next best thing is a bit of Gilbert and Sullivan, so I might try him on some of that as well if he has the patience to listen.
I'm sure that somewhere it should be possible to work in some history of music, working through different composers, and even expose him to music theory and see if that helps or hinders his tune-writing efforts.