What are the classic jokes in the music field?

It is said that a student who composed music could never write a symphony. His homework was due the next day, so he went to ask his professor how to write a symphony in one day. The professor estimated that he was drunk at that time and said, "There is only one way, that is, you take a symphony and copy it backwards, taking the last note as the first note, and copying it backwards is a symphony. The symphony has four movements, just turn it upside down. " He said, "Great, thank you, Professor." When I went home, I only found the professor's symphony, so I copied the professor's works backwards and handed in my homework the next day. As a result, when playing this piece, it turned out to be Beethoven's fifth symphony. It turns out that the professor's job is to copy Beethoven's works backwards, and the students copy them backwards.