My opinion is that singing along is perfectly normal during the uptempos, but be respectful to Kelly and the other people who paid to hear her during the ballads and quiet down until the end of the song when you can be as loud as the hell you want (cool points to anyone who gets that reference). I do not wanna hear a quintet of drunk guys yelling out "KELLY SING YOU FOUND ME!!!!" during Why, and I bet a lot of other people in the audience feel the same way.