I am looking forward to presenting a paper titled “Chromatic Saturation in J. S. Bach’s Music: Analytical and Theological Implications” at the Rocky Mountain Society for Music Theory (April 15-16, 2011, Colorado Springs). The bulk of the paper looks at appearances of the “Passion Chorale” (“O Sacred Head, Now Wounded”) in Bach’s St. Matthew Passion; the final harmonization uses all 12 pitches of the chromatic scale. So, I propose that Bach uses the entire chromatic collection to signify consummation and to underscore the theological weight of the death of Christ. Martin Luther wrote: “By this deed the whole world is purged and expiated from all sins, and thus is set free from death and every evil.” This perspective on Bach’s use of the chromatic collection is quite different from that of most scholars.
Interestingly, this presentation comes near the end of Lent, when our thoughts begin to turn to Palm Sunday and the events that followed. You can hear a choir sing the four different harmonizations of the chorale here: