First of all, let me make something clear. This article is not intended to be research-based, unlike the others I’ve written about the Mozart-Süssmayr requiem. These are just my impressions of the Sanctus and some insights into the relation between the music and the use of the Sanctus in the Catholic liturgy, as well as Catholic beliefs. I will explain why some of these “strange” harmonies, often criticized by musicologists, actually make sense when put into a theological context.
The basics first: I think the key of D major for the Sanctus makes perfect sense. Richard Maunder, one of the modern completers of the requiem, claimed that Mozart would have chosen C major for the Sanctus. His edition contains no Sanctus and Benedictus because they have nothing to do with Mozart. He retains the Agnus Dei because he believes there is Mozartian material in it, but this is a completely different topic.
The choice of D major for the Sanctus makes sense because the theme is taken from the Dies Irae:
The themes of the Sanctus in the liturgy contrast with the themes of the Dies Irae:
Sanctus, Sanctus, Sanctus, Dominus Deus Sabaoth, pleni sunt coeli et terra gloria tua. Osanna in excelsis. [Translation: Holy, Holy, Holy, Lord God of Hosts. Heaven and earth are full of Thy glory. Hosanna in the highest.]
Dies irae, dies illa, solvet saeclum in favilla, teste David cum Sybilla. Quantus tremor est futurus, quando judex est venturus, cuncta stricte discussurus. [Translation: Day of wrath, day of anger will dissolve the world in ashes, as foretold by David and the Sibyl. Great trembling there will be when the Judge descends from heaven to examine all things closely.]
Similarly, although the Sanctus makes use of the same musical theme as the Dies Irae, the difference between major and minor creates a contrast. The God that is wrathful to the damned on Judgement Day is also the same God (therefore, same musical theme) who is holy and glorious for the saved. Therefore, the major-minor difference provides a difference between wrath and holiness, reflecting the liturgy, and same theme represents that it is the same God.
Now we must turn our attention to the heavily criticized C-natural at “Pleni sunt coeli.” We have to think about the entire structure, as well as the text, of the requiem. In the Sequence (Dies Irae through Lacrimosa), the text shows a person asking for God’s mercy, particularly in the Recordare (English translation):
“Recall, sweet Jesus, ’twas my salvation brought about Thy Incarnation, abandon me not to reprobation. Faint and weary hast Thou sought me, on Thy cross of pain hast brought me, let Thy suffering be not in vain. Final Judge of Justice, Lord grant Thy absolution before the day of retribution. Guilty, now I pour my moaning, all my shame and anguish owning spare, O God, Thy suppliant groaning. Thou the sinful woman savedst; Thou the dying their forgavest; and to me a hope vouch-safest. Worthless are my prayers and sighing; yet, good Lord, in grace complying, rescue me from fires undying. With Thy favoured sheep, O place me, nor among the goats abase me, but to Thy right hand upraise me” (Mozart Requiem Translation).
In the Offertory, they are praying for the salvation of others.
“Lord Jesus Christ, King of Glory, deliver the souls of the faithful dead from punishment of Hell and from the bottomless pit; deliver them from the mouth of the lion; nor suffer the fiery lake to swallow them up, nor endless darkness to enshroud them. But let Thy holy standard bearer Michael lead them to the sacred light, as once Thou promised to Abraham and his [descendents.] We offer Thee, O Lord, our prayers and sacrifices of praise: accept them for those souls whom this day we commemorate: let them pass, Lord, from death into life, as once Thou promised to Abraham and his [descendents]” (Mozart Requiem Translation).
The Sanctus, Benedictus, and Agnus Dei are not only part of the requiem mass, but also part of the Ordinary of the Mass, though for the Agnus Dei, “miserere nobis (have mercy on us)” is changed to “dona eis requiem (grant them rest)”, and “dona nobis pacem (grant us peace)” is changed to “dona eis requiem sempiternam (grant them eternal rest).”
The text of the Sanctus calls for music that, unlike the previous sections, is not sad or desperate. Following the liturgical themes introduced in the Sequence and Offertory, let’s assume that all the saints and angels in heaven are saying, “Holy, Holy, Holy, Lord God of Hosts. Heaven and earth are full of Thy glory. Hosanna in the highest!” For those who believe in heaven, they’d probably think that heaven is so “beyond this world” that they wouldn’t really know what to expect yet.
Who would be expecting a C-natural in the D major Sanctus? It comes as a surprise, like the saved are thinking, “Wow! What a wonderful surprise! Heaven is better than I thought!”
Of course, there is no way to know if Süssmayr intended the Sanctus to be this way, or if he was using the C-natural to modulate to E minor (there is a D-sharp in the tenor right after the basses sing C-natural). Many musicologists assume the latter and criticize the harmony, but if Mozart had written it, they would probably be praising his boldness and daring. Whatever the reason for the C-natural, it makes sense after being put into a theological context.
The Sanctus and Osanna fugues have long been criticized for their brevity, and many modern versions (by Robert Levin and Duncan Druce in particular) have lengthened them in their own editions of the requiem. Although their fugues, musically, are more developed and much longer, it doesn’t make as much sense liturgically.
The Sanctus was always short in the Viennese Mass tradition because the Benedictus would act as an Elevation motet, and the Elevation of the Host could not be long delayed. The Canon of the Mass (the Prayer of Consecration) began immediately after the Sursum corda and Preface. Süssmayr (a Catholic) probably knew exactly what he was doing by not delaying the Benedictus with a longer Osanna fugue.
Mozart almost never wrote long Osanna fugues in his own masses. The brevity of Süssmayr’s Osanna is only a problem when it is compared to the double fugues in Mozart’s Mass in C Minor, but the C Minor Mass and the Requiem served completely different purposes.
Some musicologists complain that Süssmayr overused the drums in the Sanctus, but this can be explained theologically as well. My thought is…why not? Think about the text again. Wouldn’t the drums make perfect sense to show the glory of God?
Of course, these are just my own thoughts. Of course, there are undeniable musical shortcomings in the Sanctus, but I can suffer a few parallel fifths if the music corresponds with the text liturgically and theologically. In my opinion, the meaning the music demonstrates is more important than any technical rules of composition.