The Fantasia on the Choral "Wie schön leuchtet der Morgenstern" is based on the eponymous hymn Lutheran, one of the most famous of the period of Epiphany. The subject is the star that guided the Magi to Bethlehem.
Starting from the cantus firmus of the hymn, Buxtehude composed a fantasy in most sections, particularly long, characterized by the use of different media, such as the use of figures of speech and use plenty of repetition and echo effects. The first section (lines 1-29) begins with the melody of the hymn set out from the bottom, with a subsequent shift to soprano (lines 30-57). Follows a section in stylus phantasticus (beats 58-72), with rapid successions of sixteenth notes and triplets.
After a very short off richly decorated (bars 73-75), the composition continues with a jig in 6/8 (lines 76-134), followed by an episode in fugue style (lines 135-168). The opera ends (bars 169-196) with displays of new thematic material, in the form of fantasy. In the last four bars the score includes the use of the pedals.