Mozart’s abandoned ‘great’ Mass in C minor (K427) is even more of an enigma than his unfinished Requiem. He must have worked on its score some time between his marriage to Constanze Weber at Vienna’s Stephansdom (August 4, 1782) and writing in a letter to his father (January 4, 1783) that he was halfway through the composition of a Mass. Nobody knows why Mozart abandoned what appears to have been a plan to set the entire Latin Ordinary; perhaps he realised its ornate blend of Italianate operatic solos and Handelian choral fugues was unsuitable for liturgical use in the wake of Joseph II’s austere clerical reforms, which had pressured almost all churches in Austria to reduce and simplify their music-making to more modest proportions.

Masaaki Suzuki speaks with gently glowing enthusiasm about Mozart’s score, the issues raised by its incomplete state and his hopes that this new recording for BIS is an insightful artistic interpretation. We meet just around the corner from the Barbican during a weekend residency of Bach concerts and events, and I wonder if Suzuki senses an affinity between Mozart’s most ambitious sacred work and the contrapuntally-grounded aesthetic of the Baroque choral repertoire that has hallmarked Bach Collegium Japan’s career so far. ‘There is the famous story that Mozart was much affected by hearing one of Bach’s motets during a visit to Leipzig, but that was some years later than the C minor Mass was written. In comparison, Mozart’s music can look so simple on the page, but in other ways the C minor Mass has some fascinating parallels with the B minor Mass: choral movements with incredible polyphonic structure, a wonderful contrast between its movements, and of course a beautiful “Et incarnatus est”!’

Mozart never finished the string parts for this rapturous soprano aria featuring a concertante trio of flute, oboe and bassoon – which raises doubts about whether he ever performed it. Suzuki chuckles and suggests ‘maybe the missing string parts could have been filled in by Mozart improvising at the organ? At least that’s what I want to think – that it was somehow performed in Salzburg in 1783, even without the strings.’ Considering that Suzuki has an excellent woodwind trio and Carolyn Sampson at his disposal, is this a moment where he allows himself to luxuriate in such incredibly radiant music? ‘It’s important to capture the emotion, but of course it shouldn’t be self-indulgently slow. We tried to allow the music to have a natural flow: it needs a very heavenly sound as if it’s floating in the air – like breathing in and out – and these upward sequences rising higher each time are a meaningful dialogue between the voice and the concertante trio – not a competition but a harmonious unity.’

Many more problems in the sources mean numerous details have to be decided by editors, each one of whom has varying musicological agendas and their own personal ideas about what Mozart might have envisaged. Accordingly, there is no such thing as ‘the’ score of the C minor Mass, but several alternative editions that present radically dissimilar completions of missing orchestra parts; moreover, some editors attempt to reconfigure some choral passages into double-choir versions, and some have even attempted to complete the entire Latin Ordinary by providing music for the rest of the Credo and adding a plausible Agnus Dei. Suzuki compared several of these different editions before making a choice. ‘I decided to follow Franz Beyer’s edition [published by Amadeus: 1989] – although I don’t much agree with his addition of an Agnus Dei that recapitulates the Kyrie music, so we only present the movements that Mozart wrote music for. I have conducted the work using different editions in the past, and I thought in some places one edition’s ideas are better than another one, so for the recording we made a few very small changes to little orchestral details that we liked better.’

Of course, some things are fixed with more stability in Mozart’s original autograph score but are still open to contradictory artistic interpretations. We discuss the imposing double-chorus ‘Qui tollis’, and how different conductors interpret (or misinterpret) the Largo marking, Suzuki enthusing ‘this is very clearly modelled on the Baroque tradition we know from Bach and Handel, and in their time there was often a dotted rhythm for “Qui tollis peccata mundi”, where the text talks about sinfulness, and the dotted rhythm conveys the punishment and authority of the king – in other words, God’s judgement on sinners. I think Mozart probably takes one step further than his Baroque forbears and wants an even sharper energy. The dotted rhythms in the strings mean you can play with or without rests, but this is deliberately a very old-style Mozart has chosen, and I think the use of rests is incredibly important – the strings have to detach their notes. It’s also in places like this that the German pronunciation of Latin helps quite massively: “Qvi tollis” rather than “Kwee tollis”. It gives the up-beats more definition and energy. The same thing is true with the hard “g” in “[Gratias] agimus tibi”.’

As we share our mutual admiration at many passages in the score, Suzuki enthuses about how Mozart’s use of structure in some movements is close to classical sonata form. ‘“Laudamus te” is so theatrical, and I love the recapitulation when the strings gradually lead us back to the exposition theme, with the singer sneaking in on a long note that evolves into the return of the original theme. I think after Mozart it became an increasingly difficult challenge for the next generation of composers like Beethoven to find fresh and inventive ways to produce a recapitulation. Before Mozart it was easy to just begin the first idea again, but for Mozart sonata form became a useful package for communicating ideas.’ Those ideas, of course, can also be profoundly emotional – contradicting Stravinsky’s infamous barb that Mozart’s church music was little more than superficial confectionary. Suzuki agrees: ‘For me, the fascination of Mozart is that even when there are sometimes quite complicated polyphonic lines, his music always comes easily into your heart, and feels spontaneous, natural and honest.’

With the enormous project to record Bach’s complete vocal works very nearly finished, and both of Mozart’s largest sacred works now under his belt, I ask where Suzuki’s interests will take him next. ‘Actually I’ve always been interested in settings of the Mass that were not necessarily designed with only a liturgical purpose, but that might have been at least partly concert music that stretched the creative invention and skill of the composers. Maybe you can say this for several works we have recorded during our career: Monteverdi’s Missa In illo tempore, Bach’s Mass in B minor, and now Mozart’s Mass in C minor. So the next logical step is Beethoven’s Missa solemnis.’

This article originally appeared in the December 2016 issue of Gramophone. To find out more about subscribing to the world's leading classical music magazine, please visit: gramophone.co.uk/subscribe