My Girls are Nuts

The other day I found my girls in their room playing a concert on a recorder. They would take turns, one would sing while the other played the recorder, and then they would switch. They were performing the song "Behold" (it's a kids' hymn I suppose, and it goes "Behold, behold, I stand at the door and knock, knock, knock..." it's Isabella's favorite). And then when they finished they started doing "exercises" as seen below...