Fair Use is supposed to allow you to sing songs that are not in the public domain. Weird Al did it. People do cover songs all of the time. The problem is that YouTube violates Fair Use. If it was a real legal case, the alleged copyright claimants would take the alleged copyright infringers to actual court. See, virtual Google Court is not tangible. It is not real. Yes, people don't like spending millions of dollars fighting in court. I understand that. I'm just saying that the "PUBLIC DOMAIN ARGUMENT" is possibly misleading because Fair Use allows for parodies, covers, etc, according to many people, many sources.