This improvisation is part of the private Christmas concert, which I played at home for my family and neighbours back in 2013 (so these were my first steps with GrandOrgue). Since I signed up at ContreBombarde after Christmas in 2014, I found that it was too late to post it then and decided to postpone the upload until this year's Advent season -- now here it is.
It is inspired by Garth Edmundson's Toccata "Vom Himmel hoch", which I found to be a very powerful transcription of the original Christmas carol.