For decades the Missa solemnis was a major part of what Nikolaus llarnoncourt called his personal "Beethoven problem". Together with the tricky but ultimately visionary finale of Fidelio and the erratic block that is the Ninth Symphony, the Missa solemnis was one of those works to which he struggled for a long time to gain access. As a cellist with the Vienna Symphony Orchestra he got to know it in seven different interpretations, not one of which seemed to him to do it justice. lfle did not conduct the Missa solemnis himself until 1988, the year in which he first conducted a stage production of Fidelio at the Hamburg State Opera. It was during his detailed preparations for a performance with the Residentie Orkest of The Hague at the Schubertiade in Feldkirch that - as he later recalled - "the scales fell from his eyes". "All that had seemed to me to be empty bathos suddenly turned into its opposite."
The next step occurred at the Salzburg Festival, where Harnoncourt made his belated début in 1992, conducting the Missa solemnis in the Großes Festspielhaus - he always believed that important sacred works should not be confined to churches, a belief that in this case was doubly justified, for quite apart from the fact that a work of such vast dimensions as this would far exceed the scope of even the most festive solemn mass, not even the work's first performance took place in an ecclesiastical context, for all that it was dedicated to a high-ranking member of the church, The product of a lengthy genesis extending from 1817 to 1823, it was dedicated to Beethoven's former pupil and friend, Archduke Rudolph of Austria, and was intended to mark the latter’s enthronement as archbishop of Olomouc. It may be mentioned in passing that Rudolph was the youngest brother of Archduke Johann, Harnoncourt's great-great-grandfather.
One of the secrets of Nikolaus Harnoncourt's interpretation was his ability to develop this monumental work from silence, keeping the usual frenzied sonorities within bounds and allowing the individual voices to emerge from the overall textures whenever they needed to be heard on their own. When the words "Pleni sunt coeli" in the Sanctus are sung not by the chorus but by the soloists, as Beethoven originally notated them, then the impact of the message is increased.
As far as this message is concerned, few other conductors were as conscious as Harnoncourt of the meaning of the Mass's words, with the result that he always ensured that the manifold interpretative possibilities concealed within the latin text were carefully aligned with the music. The subtle distinctions in the musical message that resulted from this knowledge rested in part on the conductor's extremely careful approach to Beethoven's deliberately detailed dynamics, which were always taken seriously, their apparent contradictions notwithstanding. This often meant a good deal of experimentation in the rehearsal room. At the same time Harnoncourt's "tempo dramaturgy" always resulted in a coherent structuring of the work and in a natural eloquence.
Beethoven notated some thirty different tempo markings for his Missa solemnis - almost as many as in one of Mozart's operas. But unlike Mozart, Beethoven does not return periodically to a "basic tempo", for most of his tempo markings are used only once, and he appears to have been concerned to ensure that his wishes were expressed as precisely as possible. At the start of the Kyrie, for example, with its alla breve marking, we find the performance marking Assai sostenuto. Mit Andacht (Fairly sustained. With raptness), while the start of the Sanctus, in 2/4-time, is marked Adagio. Mit Andacht. The second section of the Benedictus bears the instruction Andante molto cantabile e non troppo mosso. There is something unusually furious, by contrast, about the presto ending of the Gloria and the chorus's desperate cries in the Agnus Dei.
The final stage in Harnoncourt's engagement with Beethoven's key work came in the summer of 2015, when he conducted it at the styriarte Festival in Graz - the source of the present recording - and at the Salzburg Festival. In this way it became the coping stone on the career of the conductors great adventure with his Concentus Musicus and with the Arnold Schoenberg Chor, an adventure that came to a sadly premature end in March 2016. These two ensembles came closer than any others to the conductors intentions, having internalized his working method and learnt to implement his instructions right down to the very last detail. ln this way what comes from the heart goes back to the heart.

The interview that follows took place in May 2015.
Herr Harnoncourt, could the Missa solemnis be likened to an attempt to prove the existence of God through music?
Beethoven would never have attempted to do any such thing. Proving the existence of God would spell the end of any faith, any religion. On the other hand, it could be argued that all art - and music in particular - represents an engagement with the transcendental. I have the impression that Beethoven was constantly flirting with the incomprehensible, opening up unexpected approaches and making the invisible visible or, rather, audible. We are guided through so many transformations that by the end of the process we ourselves could be said to have been transformed.

In writing this work, Beethoven engaged with the words of the latin Mass in an entirely personal and unprecedented way.
Above all, Beethoven draws on what stylistically speaking is the archetypal basis of all church music, time and again stressing what the church modes have to offer him and emphasizing the importance of mastering questions of musical rhetoric. The result is a unique work: there had been nothing like it previously. Every section of the Mass is interpreted in a novel way. But for us today the work no longer sounds unique: we have heard it all before. The difficulty of performing it consists in rediscovering this "unheard-of" element and allowing us to experience it for ourselves as if for the very first time.

When you conducted the work in Salzburg in 1992, you used natural trumpets, early trombones and an old set of timpani. Now you are performing it with the Concentus Musicus. What difference does this make?
The stringing of the string instruments plays an important role because the way in which the overtones are built up and the sound mixture that you ind with gut strings are entirely different. And with early woodwind instruments you get a much more differentiated sound in terms of their sonorities and keys, something that over the years has been lost. With a modern Boehm flute, all of the holes are the same size, so you can no longer cover them with your fingers alone and they need to be fitted with keys. Every note and every key sounds the same, there are only "false" intervals. Above all, there is no longer a pure third. Or take the clarinets: in his Missa solemnis Beethoven demands clarinets in A, B flat and C, but no orchestra uses clarinets in C any longer. Today everything is a transposed major or minor, and few listeners are aware any longer of the characteristics of the different keys.

The Missa solemnis is in D major but it modulates via E-flat major to the relative key of B minor. What does D major stand for?
D major stands for dominion, kingship and God, The intervals are relatively pure. D major is the key of the trumpets, which were in any case the privileged instruments of rulership.

Which pitch do you and the Concentus use for Beethoven?
a'=430 Hz. This is substantially lower than is usually found today. But this is the pitch that Verdi demanded even for the late 19th century.

Does the lower pitch not remove some of the excess pressure? After all, the risk factor in this work always relies on the sense of pathos and hysteria...
You can't get round that problem. It's still very high for the sopranos. Beethoven could be said to have written failure into his score, and he did so in a way that you can actually hear. He wanted to demonstrate the impossible. In the case ofthe strings he writes notes that are no longer on the fingerboard and which effectively have to be snatched from the air. The clarinet and the horn, too, have notes that can no longer be produced - and there are dynamic instructions that appear to be unrealizable. When the horn plays a high C, it's a natural note that is normally fairly loud. But Beethoven demands that it be played pianissimo or even pianississimo. What are we supposed to do? You need a ruse! You encounter problems like these at every turn.

For listeners, the idea that failure is written into the score is perhaps best illustrated by the vocal soloists, where there is often a problem with stamina.
That's the question. The problem today is partly based on the fact that modern performance practice no longer acknowledges a piano marking. We know how furious and desperate Beethoven was when conductors ignored his dynamic markings - he wrote at some length about the performance of his Second Symphony at a time when his hearing was not yet completely wrecked. He regarded all attempts to reduce his dynamics to a single level as a garbling of his work. We have to approach this matter with great care. Although this doesn't only apply to the instruments, it's certainly easier with period instruments.

Beethoven's setting of the Agnus Dei strikes me as particulalrly remarkable. Although this section has only six lines of text, Beethoven creates a vast, two-part movement that lasts almost as long as the Gloria, with this alarming battle painting that culminates in the plea for peace...
In most settings of the Mass, the "Dona nobis pacem" is interpreted in such a way as to suggest that peace already exists. And yet the words mean that it is not peace that reigns but catastrophe. Beethoven does not say "Thank you!" but "Give!" This is particularly thrilling in the Missa solemnis. For me, this begs the question as to whether peace can exist at all. I see this psychologically. Of course, memories of the Napoleonic Wars were still fresh in people's minds at this time, and you may even be able to see a burning city in the music. But the battle painting tends, rather, to depict the conflict that goes on inside us. It is a plea - as Beethoven himself said - for "inner and outer peace". And it strikes me as far more plausible that it is the inner conflict that constitutes the actual drama. The inner aspect is more important than the outer one. But this is true of each and every one of us.