The Teldex studio is not an easy place to find: seemingly beyond the reach of the average satnav, it perplexed more than one Berlin taxi driver during my visit. The route, though circuitous, was certainly scenic. ‘Leafy suburb’ may be a cliché but it perfectly sums up the area in which this venue nestles. The building itself, as producer and recording supremo Martin Sauer explained, was originally a dance hall before the war. Then it was a recording studio, and then, as Sauer said with an eloquent hand gesture, ‘Warner sold Teldec’.

I arrived for the final day of sessions for the record label Harmonia Mundi: six whole days were being spent recording Schumann’s three piano trios – just one-and-a-half CDs’ worth of music. At the end there were 1119 takes for the three pieces. Clearly, something exceptional was afoot. As Sauer explained, ‘We did the slow movement of the First Trio yesterday. They said, “That’s good”, then we spent three hours on it. But it’s recording – you may as well go as far as you can.’

But then these are no ordinary musicians. The trio of Isabelle Faust, Alexander (Sasha) Melnikov and Jean-Guihen Queyras (German–Russian–French Canadian) is one to reckon with. Their Beethoven trios disc for Harmonia Mundi (featuring a glorious Graff fortepiano) was on last year’s Gramophone Awards shortlist. None of them is a stranger to awards ceremonies – who could forget the Gramophone Award-winning traversal of Beethoven’s violin sonatas by Faust and Melnikov from 2010? Or more recently Queyras’s equally lavishly praised cycle of the same composer’s cello sonatas, not to mention earlier discs such as his Ligeti Cello Concerto with Boulez? What makes this line-up so fascinating is that it’s all about challenging perceived notions. Not by grandstanding or by dogmatism, but by a sense of exploration and of taking nothing for granted. That’s as true of Faust’s Bach Sonatas and Partitas and her probing Berg Concerto as it is of Queyras’s Bach cello suites (one of my favourites of all time) or Melnikov’s way of painstakingly dissecting a piece and then putting it back together again so you hear it as never before, as witness Shostakovich’s piano concertos. None of them is a period-instrument specialist as such, yet all apply elements of this practice to everything they approach. The three were already hard at work when I arrived at the sessions. Three more contrasting personalities you couldn’t imagine, yet somehow their differences gelled to extraordinary effect.

As I enter, they’re recording the slow movement of Schumann’s Second Trio. The details of how to phrase a particular motif becomes the subject of intense discussion. Faust’s gut strings are doing exactly what gut strings are famous for doing: playing up. ‘I didn’t know I was so strong,’ she mutters as one pings hard against the varnish of her ‘Sleeping Beauty’ Strad. Melnikov, seated at a surpassingly beautiful Streicher instrument from 1847, is the precise one: every take he checks against the metronome. Somewhat incongruously there’s a mascot on the piano. It later transpires, after some digging, that this is Bernd, one of three creatures with whom Melnikov habitually travels. ‘He loves doing press interviews and coverage,’ he jokes.

Martin Sauer, conducting from the control room, is encouraging, addressing each in a different language – Queyras in French, Faust in German, Melnikov mainly in English. The players describe him as ‘a phenomenal midwife’ – to Queyras he is the Grand Priest. There’s much discussion about whether there should be a ritardando at bar 33. Detail is everything, but equally so are long takes: despite the stop–start nature of the recording process, the musical thinking is seamless. That Streicher sounds as alluring as it looks, too, with moments such as the passage where Schumann breaks out into semiquavers appearing more pellucid than ever before. At one point Queyras suggests that a balance is needed between being exact and ‘aah’ – gesticulating to make his point. And the final bars, with their sighing phrases from the string players, are breathtaking – all the more so for being vibrato-free.

This is the first time that the trios and the concertos have been recorded as an entity on period instruments. Each trio will be coupled with a concerto with the Freiburg Baroque Orchestra under the Spanish conductor Pablo Heras-Casado and released on Harmonia Mundi – there will be three volumes in all. These particular sessions culminate with sushi and champagne, but Queyras has a crisis on his hands. He’s flying to the States the next day and has to get his Berlin bowmaker to certify the ivory on his bow to get through US customs. He dashes off across town, and we’re down to two.

I dive straight in with the question of why there are still relatively few chamber groups tackling 19th-century music using period instruments, especially given that the lighter-framed keyboard instruments help to right the essential imbalance of the piano trio genre. Sasha Melnikov ponders. ‘With an orchestra you immediately have a very different sound so you would never confuse it with a modern-instrument orchestra. With just one instrument it’s less immediately obvious. Another factor is that recording standards mean that an audience expects absolute precision in terms of intonation and so on. And period string instruments are much, much more difficult in that respect. For me personally it’s different playing on period pianos because the sound is more alive. But the majority of concert halls are unwilling to accept this because they’re afraid of people asking why something is out of tune. So the answer is that it is just easier not to have period instruments.’

Isabelle Faust adds: ‘If you play alone on gut strings, you don’t necessarily have the immediate positive effects but you do have all the disadvantages. It took us a very long time to record these trios – they’re very difficult works in any case, but playing them on gut strings makes everything more so. As a string player you really have to know that you want to do this as the advantages are not necessarily so obvious to an audience. I have some modern-playing colleagues who also tried gut strings but very few really like it. Most come back saying it’s not worth it – the risks are too great. You’re in this new world of clarity, of articulation, of a different kind of timbre for every note on every string. It’s much more difficult to play in tune and to be confident about a string’s ability to bring out a note because so much can affect it – if it’s a wet day, for example. But once you get a taste for it you’re hooked, and you throw yourself into this cold water even if the public don’t always like it.’

Difficulties notwithstanding, there must be advantages too, I suggest, not least concerning balance. ‘The Schumann pieces are so complex and also often very interwoven in register – where the bass is suddenly in the top and the violin is in the middle register,’ concurs Faust. I mention that there was a striking example of that in the sessions, at the end of the Second Trio’s slow movement. ‘Yes, exactly. And there is so much going on harmonically, so many little jewels, which here we can treasure without having to play a particular note fortissimo.’ ‘And so many overtones too,’ adds Melnikov, ‘which are drowned out by metal strings or a big Steinway.’

This brings us on to the Violin Concerto, a work which even now isn’t entirely accepted for the masterpiece it is, and which has one of the strangest histories of any work by a great composer. Initially misunderstood by the great violinist Joseph Joachim, who suggested it should not be published until 100 years after Schumann’s death – a view which both Clara Schumann and, at least initially, Brahms shared – the concerto wasn’t included in the complete Schumann edition. However, Joachim’s great-nieces Jelly d’Arányi and Adila Fachiri claimed in the 1930s to have received instructions from Schumann during a seance that they resurrect the work, which they duly did.

Faust again notes that this concerto is ‘all the time in the middle register. You have this huge octave when you first enter and then everything is playing around the middle. So you have no chance normally to cut through the orchestra.’

How much is the incomprehension surrounding his late music, not least the Third Piano Trio and the Violin Concerto, connected with people not understanding the idiom, rather than the oft-repeated notion that by this point Schumann was insane?

Faust is unwavering: ‘I don’t know exactly what happened in his head – there’s no doubt that he was a very extreme character – but I’m very sure that no one could write a piece like the Violin Concerto in a mad state.’ Melnikov adds: ‘First of all, what is mad and what is not mad? Personally, I think the Violin Concerto may be one of the greatest violin concertos ever written. I’m obviously wrong,’ he adds laconically, ‘but I never had a moment when I didn’t understand this work.’ Faust backs this up: ‘When I first learnt the piece, which was only a few years ago, I was very worried because I didn’t yet know what to do with it in all respects. This was when Sasha heard it for the first time, and he just “got” it – it was immediately clear to him what a fantastic work it was, whereas it took me time to get into it.’ As for the last movement, which is considered the weakest by many, Melnikov points out that ‘everyone plays it too fast. You can count on one hand the violinists who play it at the correct tempo.’ Faust interrupts: ‘Almost on one finger!’ But Melnikov disagrees, a veritable walking encyclopaedia of recordings: ‘No, there is you, there is Gidon Kremer, Anthony Marwood. But the way Isabelle plays this concerto is so far the ultimate performance of this work. You can always tell in a concert hall that there are people who get it and those who don’t. Having said that, I don’t think people “get” the Piano Concerto either, for all sorts of reasons. I love the work but I think it’s the least successful of the three concertos, the Violin Concerto being best and the Cello Concerto lying in the middle.’

If this seems almost perverse, Faust is quick to add: ‘He’s not just saying that – he really is convinced!’ Melnikov explains: ‘Everyone knows the story that in the 1830s Schumann was unhappy with the piano concertos being written around that time and he wanted to do something different – as he wrote, he wanted to redefine the genre. And I think that’s true of the Violin Concerto too, although he didn’t write a letter saying so. But the problem was that even the best violinists – Joachim among them – didn’t understand it. For a long time there was a feeling that the solo part wasn’t “good enough” to show off a violinist’s skills. But now we are finally freeing ourselves from a point of reference buried deep in the 19th century, which means that this concerto can be resurrected.’

He warms to his subject: ‘Schumann didn’t really have much of a professional training – he didn’t study counterpoint till he was in his 40s, for example. But his genius was so extraordinary that he could write this entire body of piano masterpieces when he was still very young, but then he made incredible progress and he studied composition seriously. And if you study something when you’re 40 years old, it’s not the same as when you’re 18. This led to a “late” musical language that is anything but crazy. There is nothing unsuccessful about this music. That idea makes me angry!’

Faust, meanwhile, objects to the long-held view that the Third Piano Trio is the least ‘successful’ of the trios: ‘It’s our favourite! And when we play all three trios in a single concert it isn’t less well received.’ Of course that might just be down to the performance, I suggest: Schumann is, after all, easily tarnished by insensitive playing. Melnikov is vehement on this point: ‘That’s true, it’s not robust, but there’s no excuse for getting tempi wrong because he puts metronome marks everywhere – and if you listen to Fanny Davies’s recordings [who herself studied with Clara Schumann] then you’ll hear that she observes these absolutely. And the advantage of authentic instruments is that they at least tell you where not to go. The proportions, dynamics and sonorities all make much more sense – you don’t have to be constantly correcting these as you do on modern instruments. If you go back to modern instruments after using period ones, you play in a different way.’

Isabelle Faust agrees: ‘Yes, and as a string player, your vibrato is immediately different.’ I’m intrigued by this, as her general lack of vibrato – in whatever repertoire she’s playing, be it Bach or Berg – is one of the most striking features about her approach. She laughs. ‘On gut strings it’s often too risky to use much – maybe it’s because I’m an amateur gut-string player!’ Adds Melnikov with a glint in his eye: ‘I started to play with Isabelle all those years ago because she was the only one not using too much of this horrible vibrato! Today’s it’s used like soy sauce in a bad Chinese restaurant: it’s everywhere. There’s nothing wrong with vibrato – in fact I love it – but too much can be annoying!’

Faust recalls a seminal experience when, as a 16-year-old, she performed for Christoph Poppen, with whom she was hoping to study: ‘I went and played a Mozart concerto for him, and he said, “Can you now play that non-vibrato?” I thought this was akin to him asking me to play just open strings or to hold the bow completely differently – as if it were something technical. I was stupid back then. But he was the first one to tell me – and even today very few modern-instrument teachers seem to talk about it. But vibrato is, after all, only a form of ornamentation.’

Another vexing question for these exacting players is that of scores. Faust says regretfully that they weren’t able to get at the manuscripts of the trios. ‘We used the Henle versions and looked at the first edition. With the Violin Concerto, I started to learn it before the first Urtext editions came out, so I had to work from the Schott edition from 1937 – though without the emendations by Hindemith, who put some of the writing in the final movement up an octave – which was still very much changed because the piece was supposed to be unplayable. That forced me to go back to the manuscript, which happens to be here in Berlin [where Faust also lives]. From this material I tried to make some sense of it – and then, when I compared it to the newer Urtext editions, I felt I hadn’t done too bad a job!’

Similarly, for the Piano Concerto, Melnikov took nothing for granted: ‘I went to Düsseldorf, to the Heinrich Heine archive, to see the manuscript. It broadens your horizons seeing any manuscript but this one was interesting in terms of what has been crossed out. As a composer, you might bitterly regret some of those decisions, so I took the liberty of putting some of them back in: it’s mainly a matter of accents and that kind of thing. So often, even the best editions today don’t take much care about where dynamic markings are placed in terms of left and right hands, which is such a basic thing for a pianist. But then in the manuscript you immediately see from the way it’s written whether it’s something very important or just something in passing. Of course you end up having more questions than answers. But it helps to give you a better perspective.’

This brings us on to the question of Schumann’s orchestration. We’re now thankfully past the era in which he was regarded as a poor orchestrator, and it seems that, again, this is an area where period instruments truly come into their own, particularly in matters of balance and texture. As Faust says, ‘With a work like the Schumann Violin Concerto, the most important thing is to have an orchestra that is really interested in the music and loves it and wants to find out about it.’ Something that perhaps hampers something as hackneyed as the Piano Concerto? ‘But all orchestras are afraid of its last movement,’ Melnikov retorts. Faust sums it up rather neatly: ‘They think they know the Piano Concerto. And with the Violin Concerto they think they know it’s a bad piece. In both cases, they’re wrong!’

Faust found herself playing the Violin Concerto with Bernard Haitink and the Chamber Orchestra of Europe at last year’s Lucerne Festival. ‘Of course they’re a modern-instrument ensemble but it shows that Schumann works particularly well with a chamber-sized orchestra. And Bernard hadn’t done the Violin Concerto before so he looked at it as if it were a blank canvas. And there were no problems at all with the orchestration! How fantastic that, now in his 80s, a man who comes from a tradition of big orchestras is discovering that chamber orchestras can work so well for Beethoven, Brahms, Schumann and so on.’ The conservative Lucerne Festival audience loved it, but I wonder whether it even mattered to these musicians what the public thought? ‘Well we just want to get as close to what we think might be in this music, to its heart’, says Faust. But Melnikov has the last word: ‘If one really tries to be honest, one stays on the menu.’

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This article originally appeared in the March 2015 issue of Gramophone. To find out more about subscribing to Gramophone, visit: gramophone.co.uk/subscribe