@nobuzz - In America it depends on the situation. If the event has arranged a person to sing the anthem, then it is proper to listen to that person without singing. But other times, with no live performer, the audience sings. What is impressive about this is that when the mic went out the audience picked up in unison, where it could be considered a slight faux pas to sing during the girl's performance.

I didn't know in Canada that you always sing.