Ein feste Burg ist unser Gott (BWV Anh II 49)

Throughout this composition the complete melody of the hymn is played in long notes in the upper voice. The other two voices play an accompaniment of which this main motif is derived from the first 8 notes of the choral melody.
The text of the hymn praises God for being a source of power and salvation in times of trouble. And while the melody sounds, the accompaniment constantly repeats this motif, and in effect constantly says "Ein feste Burg", "Eind feste Burg", "A mighty fortress". In total (including the repetition of the first half) 38 times. It gives a solidness and firmness to the piece that is a perfect expression of the meaning of the text.

Score available on my site: http://partitura.org/index.php/johann-sebastian-bach-ein-feste-burg-ist-unser-gott-bwv-anh-ii-49/