Though the Ordinary of the Roman Catholic Mass consists of only five movements—Kyrie, Gloria, Credo, Sanctus/Benedictus/Osanna, and Agnus Dei—Bach divides the text and music of his B Minor setting into twenty-three separate movements, eighteen of which are for choir and orchestra alone. That is quite a lot of music; and with the exception of the Gratias/Dona nobis movements, and the repeat of the Osanna, each movement has different music. And all of it is great. How does he do it?
First, it is important to realize that plagiarism was not a dirty word in Bach’s time; nor was parody. Bach, and his colleagues, had immense responsibilities in the preparation and performance of music for the theater, the court, the church-- and their success depended on getting it all done, rather than on satisfying a theoretical mandate that they be original. To use a restaurant metaphor: Bach, the head chef of Leipzig or Weimar or Cöthen, was free, even expected, to build upon the successes of others, to shop for ingredients at the same markets, to use the recipes and menus that had worked well for other chefs and alter them to suit his own tastes and circumstances, even to change his own recipes over time as his needs and tastes changed. Music was a living, volatile consumer product, constantly evolving to meet demand. Creativity reflected one's ability to arrange the materials at hand, as well as to invent new materials. In other words—Bach borrowed freely and happily from other composers, as well as from himself, both because this enriched his palette of possibility, and because it allowed him to keep up with his workload. It is inconceivable that Bach could have accomplished all he did in his lifetime, were he under pressure to stay away from the intellectual property of others.
An extraordinary amount of Bach scholarship over the past century has focused on sleuthing out the sources behind Bach’s music, and in preparing new and better editions of his music, based on this detective work. Prominent names in this work, currently, include Joshua Rifkin, Robert Marshall, John Butt, and Christoff Wolff; and while these scholars frequently disagree with one another, as a group they persistently push the envelope, and contribute to general knowledge of the composer and his work. Between them, these men have determined that very little of what is now called the Mass in B minor was freshly composed for the work-- perhaps as few as four or five movements. The remaining movements were selected by Bach from music for cantatas which he had composed throughout his career. Scholars agree that he seems to have chosen music which he thought was his best work, as well as music which would suit the character of the Mass, and would reflect accurately the new, Latin texts. He transposed some movements to new keys, in keeping with the overall key structure of the new work; he adapted phrase structure to fit the new texts; he eliminated instrumental introductions and interludes, to move the dramatic action forward more efficiently; and he composed new movements, as well as sections of movements, where he needed them to balance and complete the work.
Let’s consider movements 3-6 of the Credo portion: Et in unum Dominum, Et incarnatus est, Crucifixus, and Et resurrexit. Scholars agree, based on internal evidence, that Bach adapted the duet Et in unum from an earlier composition, though that earlier duet is lost. The close imitation between the two voices is ideally suited to a love duet, probably from a secular work, and adapts easily to a text which expresses the oneness, the consubstantiality, of the Father and the Son. In his original version of the Mass, Bach set the entire text of movements three and four within this one movement. It was only in the final months of his life (determined, again, on the basis of internal evidence) that he decided he needed a separate movement to set the words “And was incarnate by the Holy Ghost of the Virgin Mary, and was made man.” So he kept the music for movement 3 intact, had the soloists repeat earlier words, and composed a completely new movement -- one of the few freshly-composed movements in the Mass, and one of Bach’s final compositional efforts. In so doing, he created a numerical symmetry which the Credo had previously lacked, placing the Crucifixus exactly at the center of this discrete section, as well as exactly at the center of all of the Mass movements which lie between the identical musics of the Gratias and the Dona nobis. It is an amazing engineering feat, which adds internal structure for the connoisseur and first time listener alike.
Bach adapted the Crucifixus movement from his cantata BWV 12, where it has the words Weinen, Klagen, Sorgen, Zagen. Butt hypothesizes that Bach could have adapted even this early cantata movement (1714) from a similar movement by Vivaldi (Piango, gemo, sospiro e peno), but goes on to say that such laments were standard literary forms, and that, together with its descending bass line, is such a standard form that it would be stretching things to suggest that Bach did anything other than compose his own version of a common form. More interesting are the final four bars of the Crucifixus; Bach added these to the music he borrowed from himself, and with them modulates to G Major (thereby setting up the D Major of the following Et resurrexit) and brings the choral forces down to the lowest pitches they sing in the entire Mass, thereby representing the lowering of Christ’s body into the sepulchre.
The following movement, Et resurrexit, explodes out of this with no pause and no instrumental introduction—voices and instruments enter with a complete change of affect, in a fanfare-like, rising triad. Scholars assume that this movement, as well, is adapted from an earlier, secular cantata—possibly the lost birthday cantata for August I, BWV Anh. 9. In adapting it, Bach dropped the opening instrumental introduction, which would have slowed down the drama of Easter morning, but included other instrumental interludes, which have a euphorically dance-like character and seem to suggest heaven and earth rejoicing.
In his handbook for the study of the Mass in B minor, John Butt recounts the experience of one of the early Bach scholars, Julius Rietz, who wrote the first published study of the sources of the Mass in 1857: “Reitz shows himself to have been a meticulous scholar, who even made enquiries into the fate of Bach’s first set of parts of the Sanctus, copied in 1724 and loaned to Graf Sporck. The inheritors of the estate informed Rietz that many manuscripts had been given to the gardeners to wrap around trees. One can barely dare to envisage what similar fates befell other manuscripts from Bach’s circle.” I expect Bach would not have been surprised by this; the archives and libraries of our modern world would probably astound him. Christoff Wolff suggests that one of the principle motivations behind Bach’s compilation of the Mass was his assumption that the thousands of pages of his cantatas cycles would not last—that they were too specific to their own time, location, and purpose to be of any use once he was gone, and that the only way he could preserve the best of his work was to use it for a Latin Mass, which would have a better chance of being saved and recognized in the future. My many years of participation in the Oregon Bach Festival has given me the opportunity to sing and study many of Bach’s surviving cantatas, but I am unusual in this experience—most performers know only a handful of them, and most listeners don’t know them at all. So from our viewpoint, Bach had it right—his Mass enables us to know not only what he was able to preserve, but also the dimensions of our loss.