A german 19th century carol, here in an arrangement of Ivor Atkins. The "Bariton" (Basson-Hautbois) sings the carol "The Three Kings" (Drei Kön'ge wandern aus Morgenland) and the choir sings the chorale "How lovely shines the morning star" (Wie schön leuchtet der Morgenstern) as accompaniment.
There are beautiful renditions of the Choir of King's College at youtube!