I had that 40/80 column adapter, later I had a bus expansion sticking out the back of the Vic so that I could have multiple cartridges plugged in at the same time, such as the vic Super Expander which added another 3k (8k?) and enhanced Basic, a few other 8k expansions, and I think there was a Machine Language monitor cartridge plugged in there as well.
This configuration was actually more functional than the C64 for a long time. I used this even after I had te 64 and didn't give it up untill getting the c128 that also had 40/80 capability and even went further--- it could display a 40 column display on one monitor, and an 80 column display on another monitor at THE SAME TIME! Dual displays baby!
At that time the poor vic was retired and became the hardware controller for an EProm burner used to copy 4k Atari 2600 cartridges.

I dont think I recall ever having any kind of music player on the Vic, I remember having "I feel fine" playing on it, but I think it was an actual basic program that generated the music.