Credo

The Credo is the longest text of the Ordinary of the Mass. As a result the musical settings of the Credo have tended to include a good deal of syllabic text set in a quick tempo; despite this, they are also frequently the longest musical movements of the Mass. The text covers all the basic tenets of Christian belief: belief in God, creator of all things; in the Holy Trinity, the Father, Son and Spirit; the birth of the Son to Mary; His death on the cross and resurrection on the third day; eternal life; forgiveness of sins, and much more. We have no idea how long Mozart’s Credo would have been, as he left it incomplete– and not even just a little incomplete. It is surprising to me that Mozart covers as much text as he does in the first movement, which is shown below.

Movement 1: Credo in unum Deum, patrem omnipotentem, factorem coeli et terrae, visibilium omnium, et invisibilium. [Credo] et in unum Dominum, Jesum Christum, Filium, Filium Dei unigentium, et ex Patre natum ante omnia saecula, Deum de Deo, lumen de lumine, Deum verum de Deo vero, genitum, non factum consubstantialem Patri, per quem omnia facta sunt. [Credo] qui propter nos homines et propter nostrum salutem, descendit de coelis.

• Mozart begins the movement with a chant incipit on the words "credo in unum Deum" (I believe in one God). This is a traditional occurrence in composed settings of the Gloria (using instead "gloria in excelsis Deo") or the Credo, tying the musical performance of these movements back to the standard practice of having the priest begin the text, with the congregation joining in shortly. In older times, the priest or cantor (selected soloist from the choir) would invoke the prayer with the little incipit, and the composer would begin his musical setting with the remaining text. It is interesting to me that Mozart then begins his setting by repeating the words "Credo in unum Deum," instead of continuing with "patrem omnipotentum"; furthermore, he has the choir repeat the word "credo" at their entrance ("credo, credo in unum Deum"). I can think of two reasons why he may have done so: 1) to reinforce the primary belief of Christianity–belief in one God (which distinguishes Christianity and Judaism from polytheists sects); and 2) to give better flow to the entire text after a long orchestral introduction. The separate chant incipit is long forgotten after the colorful introduction of string fanfares and oboe flourishes.
• Mozart adds two additional "Credo"s to the standard text here, perhaps to reinforce the idea that I believe–that this prayer is a statement of belief, and not just a litany of ideas said by rote.
• The orchestral introduction is composed of two primary ideas, mentioned above, but shown here below:

• Each of the three choral "credo" statements are set homophonically, on the first and second beats (in 3/4 time), with the soprano line leaping downward each time. Each time, the choir is accompanied solely by strings and organ, with those instrumental parts reiterating the opening fanfare idea. This not only puts the emphasis on the word "Credo," rather than on the orchestra; it also serves as a unifying device throughout this first movement.
• Mozart changes the texture for the first time at "et invisibilium." Here, the rhythmic unison of the choir is sudden dissolved as individual voice parts come in (SI, SII, T, B, A order), creating a layered effect as each part sustains syllables of the word "invisibilium." Over time (just a few measures, really, but it seems longer because the rhythm of the voices has been considerably lengthened), the music turns more chromatic, signifying the mystery of the invisible God who is so present in all things visible to humankind. But this momentary darkness (ms. 28-29) does not last.
• The second section of text begins with a new statement "Credo", this time in the dominant key of G major. Thus, tonal convention of Mozart’s time factors here in delineating the musical form of the movement. (It was typical of Viennese Classical works in major keys to move from tonic to dominant, then to wind their way eventually back to the tonic.)
• But G major is just a gateway to another tonal world for Mozart, who in the next passage of text and music moves to a minor (relative minor of C major). This comes at the mention of Christ’s being begotten from the Father for all. While we do not yet hear of Christ taking man’s form, suffering, and dying, the turn towards minor reminds us that this is coming: Christ was begotten from the Father….God gave His only Son to this world, and allowed him to die a horribly, untimely death, that mankind might have hope for eternal life and happiness. We rejoice in God’s great gift, but we live with the knowledge that it was mankind’s own sin that will cause God (in a few verses) to sacrifice his Son for us. The basses, meanwhile, state four times "credo" while this tonal transition takes place. What is the cause of their insistence?
• The next few verses and phrases continue to explore the minor mode–through a tonal sequence, we go from a minor, to d minor, to g minor, to c minor (overall tonic key of the Mass). This section, which takes us textually from "Deum de Deo" to "facta sunt" (see above). The music cadences on "facta sunt" on a G major triad, dominant to both C Major and c minor…we wait in anticipation to see to which key Mozart will resolve the music.
• The answer is…C major. With the return to C major (m. 84), we have a clear sense that, in terms of musical form, the preceding section served as development function, with increased instability, movement away from (rather than towards) the tonic key. The previous section is rhythmically unstable as well, overlapping (and seemingly competing) text statements by the women and men; furthermore, the string fanfare is significantly reduced and the soothing oboes are totally absent.
• The return to C major is followed shortly thereafter with a reprise (m. 87) of the opening choral statement, this time using the text "credo qui propter nos homines." This gives a sense of a ternary structure for the movement (A B A’).
• Mozart turns the music away from C major once again, this time mirroring the previous move up to G (up 5 in terms of tonal relations) with a move down to F major (down 5). He is careful to save this move for the text "descendit de coelis" —he descended from heaven. Thus, as Christ moves down from heaven to earth, the tonal relation moves down 5; Mozart reinforces the descent with descending melismatic lines in the soprano parts a few measures later:

Movement 2: Et incarnatus est de spiritu sancto, ex Maria virgine et homo factus est.

• This movement contrasts the first in almost every way. It is set in 6/8, a compound duple meter (instead of 3/4, a simple triple meter), F major (instead of C major), uses solo soprano (instead of SSATB choir), clearly intended as an andante movement (instead of allegro maestoso), and accompanied by solo flute, oboe, and bassoon along with strings (instead of pairs of oboes, bassoons, and horns, plus full strings).
• The "et incarnatus" section of the Credo always appears to be a favorite movement for composers, probably because of the focus on the birth of Christ, rather than on His death. Mozart takes a gentle approach here, as many composers do, writing for solo soprano–is this not just a representative from the choir (congregation/humanity), but also perhaps Mary singing to her newborn child? The intimate movement for reduced orchestral forces and solo voice, set in F major and 6/8 meter, has a delicate flow to it. It has been called a "sicilienne" in some cases, a pastoral in others.
• Mozart links this movement to the previous with the allusion to F major key near the end of the preceding movement. In addition, it is a favorite key of Mozart and other composers in trying to portray pastoral settings, or in reflecting pastoral scenes or people. (Beethoven, for example, uses F major as the primary key for his Symphony No. 6 (Pastoral).)
• The solo line requires delicate but versatile singing, which can support the intimate feeling on the one hand, while performing the difficult ornamentation Mozart has written for it:

• The most beautiful portion of this movement may be Mozart’s written-out cadenza for solo soprano, flute, oboe, and bassoon. The orchestra reaches a fermata on a second-inversion I chord (the standard chord held by the orchestra to signal a cadenza), as the soprano sings the "fa" of "factus est". The entire cadenza is sung on her "ah" sound (the perfect vowel for sustaining). It is twenty-one blissful measures of melodic interplay among members of the solo quartet. The chamber orchestra then closes off the movement without the soprano (typical of what would happen after a cadenza in a solo concerto of the time).