How do you buy songs at the shop in Animal Crossing

you can't buy songs in animal crossing. What you have to do is go to the museum and go into the coffee shop called The Roost. Then you will see a white dog playing the guitar on the small stage. tap on him and he'll have 2 options for you. One of them is a request and the other one is random tap on the random one. After the song he will give you a CD. that is the song he just played. You HAVE to do this at 8:00 on Saturday. If you do it before 8:00 or another day this won't work.