Zachow wrote at least four preludes based on the melody of "Vom Himmel hoch da komm ich her". Three can already be found on my site. Today follows the fourth. The chorale melody is played with the right hand, though it might be difficult to discern it. In the rapid passage work Zachow writes the chorale notes are consistently every first note of a group of 8 sixteenth notes. Difficult to hear, easy to see with the score in front of you.