So, you're sitting in a concert and everyone is being quiet and listening to the musicians. A chorus comes along and you start booming it out. Why??? Even if no one else is singing? If you haven't been invited to sing? What about if the musicians want to arrange the chorus differently? What about if they have some beautiful harmonies all worked out and want them to be heard? What if they just don't want people singing along? Do you really think that means they are self-important? If you perform, do you really like people interrupting your performance uninvited?

Oh, and I'm really NOT a rule maker. I just think that foisting your voice on a bunch of people who paid to hear someone else's voice is rude. I'm not talking about situations where singing along is expected and part of normal behavior.