A Great Light

This well-known text from Isaiah is an example of synonymous parallelism, a technique in Hebrew poetry in which the basic content of the first line is repeated in the second with different words and emphasis.  The musical form of this setting follows the same idea.  After both lines of text are sung, they repeat with a shorter but more dramatic version of the same musical ideas that introduced each bit of text.  The rhythmic gestures are familiar quarter and eighth note patterns that give the lines a sense of plodding, especially with the descending bass line in the opening few phrases.  As the music walks first into darkness and then deep darkness, it modulates further along the circle of fifths using flats, all the way to D-flat minor.  As the light dawns at the appropriate places in the piece, the flats are replaced by naturals and eventually sharps, with the final bars leading us to a Phrygian cadence and a D major chord.