Bach's "Nun komm der Heiden Heiland" (BWV 659), part of the 18 Leipziger Chorale, is based on “Veni, redemptor gentium” by Ambrosius [Ambrose of Milan] c340-397. The German translation is from Martin Luther (1524). See also my upload doc below comparing translations of the hymn.
Albert Schweitzer argued -- both during his conversations with Charles Marie Widor at the St Sulpice in Paris and in lectures and writing -- that Bach's organ choral works ought to be viewed as containing elements of programmatic music - that is, music that not only attempts to depict the mood and polyphonic elaborations on the hymn or melody theme(s) it presents, but also music that contains depiction of images, parts or aspects of the text of the hymn under consideration.
The continuity of the "walking bass" in the pedals, easily recognisable as a 'steady and dignified approach of "the Redeemer",' is sharply interrupted when the Cantus Firmus presents its rich flourish of the third line of the choral. According to the Dutch Bach Society, "the world’s amazement is reinforced by a harmonic pause and an abrupt deceleration of the bass – everyone holding their breath – a trick often used by Bach when writing about the birth of Jesus." (1)
There is more. In the 4th & 5th bar of the 3rd CF line, two striking sequences of four seemingly discordant chords are arresting the rhythm, bringing the continuity to an interrupted halt. In German, the 3rd line of the first verse gives the clue: "Dass sich wunder alle Welt". The word "wunder" is used; in English this translates into notions of a "miracle", and there's an association with "wonder" as in "And I wonder how you are..." This turn of phrase activates an introspective contemplation, a meaning which is not represented in the English or Dutch translations of the hymn. The German phrase "Wie Soll Es Sein?" ("How Can This Be?") comes to mind; it makes me think of the Matthew Passion opening choirs!