Georg Böhm wrote two pieces based on this Christmas hymn: a choral prelude (publisehd a year ago: http://www.contrebombarde.com/concerthall/music/22931) and this set of variations. After the choral follows a series of 5 variations. They build up from relatively easy flowing 3-part writing in the first variation to dense virtuosic 4-part writing in the last variation. A nice piece to use on CHristmas day. And a nice piece to show of different colors of an organ.