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.
“It is a far, far better thing to have a firm anchor in nonsense than to put out on the troubled seas of thought.”
“It is one thing for the human mind to extract from the phenomena of nature the laws which it has itself put into them; it may be a far harder thing to extract laws over which it has no control.”