I had a bit of C64 collection a couple of years back. It contained a "Commodore Music Maker" program with music keyboard that clipped onto the C64 to allow your to make 8-bit music. It was tully retro - ended up selling it on Ebay to some American wally for $30!
There is a big C64 following out there! I used to buy the machines for $2 at garage sales and flog them on ebay for $20 - /$50. I even obtained some C64 p0rn - it was pretty pixellated but if you squinted hard you could see pictures .