You’ve all seen the flashmob events made famous by Improv Everywhere, for example, Grand Central Station in New York. Here is a group doing the same thing  in a Moscow shopping mall singing a popular Christmas carol. The singers are from an Orthodox boarding school and include clergy (obviously the bearded ones).

[youtube=http://www.youtube.com/watch?v=JPlZTqc5z7o]

A bit late for Christmas, I know, but just came across it.