Even if it was a difficult operation to copy a song, it only takes one person to do it. After that the spread of the song via the Internet or other means of propagation is only limited by the honesty of the users.
“I'm more influenced by my own interests than anyone else's. Writers have to entertain themselves, or they can't entertain anyone else.”
“Art is the most beautiful deception of all. And although people try to incorporate the everyday events of life in it, we must hope that it will remain a deception lest it become a utilitarian thing, sad as a factory.”