Talk:Leap of Faith/@comment-24256233-20140324204148/@comment-6025526-20140325005025

It might have been referring to production order now that I think about it. The list of numbers was made pretty far back, around the beginning of the season. The episodes were still referred to by their production order back then, not by their airing order. The airing order is usually decided after they make the episode. The production order is the order in which the episodes are made in the first place.

So since this episode is in fact 21 in production order, this is most likely the episode which will have a song.