The singers have electric lights that are shaped to look like candles. Buzz, like the other singers, starts with one, but takes another from the singer next to him and holds them up to Kevin's ears. The lights are bright enough and close enough to Kevin's ears to shine through them.
Buzz then moves the lights in a manner that imitates the use of drumsticks on a drum, with Kevin's head being where the drum would be, then resumes putting them behind Kevin's ears. Kevin turns around and pushes Buzz, which knocks him over. As he falls, his arms flail, hitting the people next to him, causing them to fall over and hit the people next to them, and so on. This chain reaction causes everyone (except, for some reason, Kevin), to fall over. They knock over a large piece of scenery made to look like a Christmas tree, which then hits the pianist.
I'm not sure how much that is referring to things you'd be familiar with; if you're blind from birth, you haven't had much use for candles, or the electric lights made to imitate them, and you wouldn't be familiar with the phenomenon of bright lights being visible through thin parts of one's body.