Before answering that question, I'll describe the Mass for you and its historical context. Early 19th century Europe was a cesspool of government-sponsored violence. The Napoleonic Wars, wars of imperial conquest, and struggles against historic empires like the Austrians and Ottoman were already laying the foundations for the World Wars of the 20th century. Beethoven's dream of peaceful and popular self-determination seemed to be moving further out of reach.
Beethoven was raised a Roman Catholic, but was non-practicing as an adult even among the heavily Catholic society of his Vienna home. Given my knowledge of him, I surmise the Roman Catholic hierarchy and Beethoven's humanist leanings weren't meshing well.
In any case, it is pretty clear he never meant for Missa Solemnis to be performed in a church. He scored it for a very full orchestra, 4 soloists, and full chorus, roughly 140-200+ musicians. Even if he had it performed in Vienna's glorious St. Stephen's cathedral, either the stained glass would have blown out or notes would still be reverberating today, 190+ years later. The full debut of Missa Solemnis was May 7, 1824, in Vienna's Kaertnertor theatre, programmed along with the debut of the Symphony No. 9. If I had a time machine this concert would be one of my first stops.
Beethoven didn't fool around with the structure of the Roman Catholic Mass at all, so the major sections are:
- Agnus Dei
The Kyrie – Kyrie eleison, Christe eleison, Kyrie eleison (Lord have mercy, Christ have mercy, Lord have mercy) is described as traditional, but I find it unlikely that Beethoven chose the ABA (theme 1, theme 2, theme 1) out of laziness or lack of creativity. That ABA structure exactly reflects the text. The B section contains some lovely counterpoint, where each group has its own melodic line that fits with the others. Counterpoint is an older Baroque form, so Maestro roots the Mass in a deep history. This also shows Beethoven as a student, and master, of composition history.
If the Kyrie is a nod to history, Gloria is a joyful, exuberant take that begins by schooling all of us on the possibilities of composing in ¾ time, or three beats per measure. It switches to 4 beats per measure after the introduction to better match the text, then, at In gloria Dei patri, Beethoven launches into a brilliant, epic, and difficult fugue. If a performer gets lost in here there is no return.
Credo – 'I believe' – starts in the key of B-flat, moves to D, then F, and back to B-flat, a musical triad reflecting the Christian creed of the Trinity. At Et incarnatus est – along with the soloists, Beethoven composes a dancing solo for the flute, the instrument of hope, proclaiming the joy and vital need for God to come and become one of us. Another fugue, faster and even more difficult, concludes Credo (and the life of the world to come) signifying the swift and total transformation from earthly life to eternal life.
Sanctus is Maestro's most well-developed and beautiful treatment of the ongoing connection between the kingdoms of heaven and earth. In it, a solo violin breaks into the music in its highest register, then floats downward in a stunning depiction of the Holy Spirit coming to earth as if gliding like a dove. The conclusion of Sanctus is, in my opinion, the most beautiful music Beethoven ever wrote and it frankly defies any description I could attempt. Just listen.
And then, the Agnus Dei. Ah, the Agnus Dei. First, a plea: Lamb of God, have mercy on us. Then comes the prayer, Lamb of God, grant us peace. The prayer is suddenly, and very unexpectedly, interrupted by the drums of war. This sacred Mass is profaned by the sound of human violence, and “grant us peace” evolves from prayer, to cry, even to shriek, before ending as a plea. Agnus Dei is raw emotion and deeply, deeply, personal, and very nearly Beethoven's musical Last Will and Testament.
So why don't we hear this brilliant music more? Why can we readily identify the “Ode to Joy” but not Kyrie, Credo, or Agnus Dei?
Yes, Missa Solemnis is expensive to program given the large orchestra, soloists, and chorus, but the 9th Symphony requires the same and it is one of the most frequently-performed classical works. Yes, it is difficult, one of the most demanding in all of choral literature. Some recordings I have heard cheat and simplify parts, but world-class performers don't avoid challenges. They earn their reputation that way.
My opinion? It's that Agnus Dei. After an hour of high spirituality delivered through utterly brilliant and transcendent music, Beethoven leaves us dirtied by human reality, leaves us with questions instead of answers.
This reality, these questions, are uncomfortable, but they are Truth. We may not want to hear it, but we live in a world that is tensioned to the extreme between the sacred and the profane, between peace and violence, between love and hate. Beethoven confronts us with this uncomfortable reality in a stunning display of art's highest purpose: to show us ourselves and push us to be better.