As a practical matter, I don't think anyone has much to worry about if they are singing around the campfire or at a festival/jam session. I'm talking about anyone who is singing for fun- not profit. While you can be sued by anyone, including a copyright holder, it just doesn't make much sense for them to do so. Copyright holders and lawyers are interested in deep pockets. When you start making money from their material, or causing them significant financial loss in some way, then you need to look out. Am I saying that you should violate someone's copyright? Absolutely not! I'm just saying that there is not a copyright SWAT team out to hassle us amatuers. You Pros earning a living at music face a different situation.

Have Fun!

OT