You can always be sure of a cheery welcome from Harry Christophers. As I enter the backstage room at London’s Cadogan Hall – where this evening he is due to conduct Monteverdi’s Vespers – he gives me the kind of good-natured hello you might get from someone you meet unexpectedly in the street rather than someone waiting to be interviewed about their work. He did it the first time I ever bumped into him – which actually was in a street, nearly 20 years ago in Palermo – and he is still doing it now as we sit down to discuss the ensemble he founded 40 years ago to perform Renaissance music, and which is now one of the world’s most famous concert choirs: The Sixteen.

As we talk about this significant birthday, it soon becomes easy to put two and two together and see that Christophers being quite possibly one of the nicest and most uncomplicated conductors in his profession has been a major factor in building the community he has with his choir. ‘The aim from the start was that we loved this music and wanted to perform it. The fact that over the years people started coming to our concerts and enjoying them, together with our growing realisation that we should be bringing it to a wider public – well, it all developed from there. But the basic principle of just loving what we were doing has never left us; it’s been the whole nature of the group. They’ve been incredibly loyal to me, and I hope I’ve been loyal to them.’

‘Today, there are so many really good singers about, and you really have to be at the top of your game all the time’ – Harry Christophers

In 1979, the Renaissance choral scene in Britain was rather different from what it is today. Now we see choirs of professional adult singers everywhere. In those times, the preferred performers of the music of Byrd, Palestrina and Victoria tended to be choirs of boys and men at colleges such as King’s, St John’s (both Cambridge) and Christ Church (Oxford), or at cathedrals such as Westminster. ‘It was all very much collegiate-based back then,’ Christophers agrees, ‘and the only professional choirs specialising in this repertoire that I can think of were the Monteverdi Choir and the Schütz Choir. But then around that time Peter Phillips founded The Tallis Scholars, and then we started up. Mind you, it was all incredibly cavalier at first. In my day you could get into Oxbridge if you could sing, or play cricket, or act, or row, or play the organ. Nowadays you have to have three A*s at A level, and you might not even get in then. (That’s a nightmare for those choirs now, by the way.) But the level of professionalism in the music world has got better and better. Today, there are so many really good singers about, and you really have to be at the top of your game all the time.’

There can be few who would dispute that The Sixteen have long been a benchmark for choral excellence – flawless in ensemble and radiating a sound that combines the vocal strength and focus of the professional chamber choir with the tonal warmth that comes from precise tuning and a carefully honed choral blend. The macho edge heard from some other high-powered choirs is tamed by Christophers, who favours instead smooth contours and lovingly sculpted phrases. To see them performing live, furthermore, is to be acutely aware of the technical assurance and musical commitment of every one of the singers – indeed, notable former members include Sarah Connolly, Mark Padmore, Carolyn Sampson and Christopher Purves. But ensemble singing is an art in itself, and while the UK is not short of highly accomplished professional singers, selection is still a special skill.

‘Obviously I book people whose voices I like,’ Christophers explains. ‘They’re all incredibly musical and stylistically aware. But I’ve always encouraged people to express themselves – it’s always been my policy to allow them to sing. That principle has never changed, but what I do think has changed is that the whole quality of voices has improved so much. The thing I noticed when we made a Christmas programme a few years ago and all the sopranos had a solo was that every one of those six sopranos had a completely different voice, there was no sense of them being uniform. But they also know how to sing with each other, support their colleagues and make it gel.’ It must be a hazardous task, I suggest, trying to find new singers who are both individual and able to fit in. ‘When a new voice joins, you can always tell whether they’re going to be there for just one concert or for the next 10 years. A lot of our key singers made their first appearance with us as a dep, and I remember Elin Manahan Thomas coming in in exactly that way – it was a Choral Pilgrimage concert live on BBC Radio 3 and she didn’t put a foot wrong, her eyes were on me and communicating, and I thought, “Yes, that’s the sort of person I want.”’

Christophers’s own background was as a singer – at Canterbury Cathedral as a boy, at Magdalen College, Oxford, as a student, and then on the professional circuit in the late 1970s as a tenor at Westminster Abbey and with the BBC Singers, among others. So what was it that caused The Sixteen to come into being? ‘Well, I didn’t really know anything about Tudor music before I went to Oxford and was introduced to it by Bernard Rose and David Wulstan and by singing in The Tallis Scholars sometimes, and part of me was always thinking, “Actually, I’d really like to do this myself.” We’d formed this fledgling group, and we thought it was time to do a London concert. So, like everyone else, we did a debut at St John’s Smith Square; I remember doing Mundy’s Vox patris caelestis.’

Not ‘everyone else’ is still here 40 years on, however. What does Christophers think made The Sixteen one of the survivors? ‘As those early years went on, I realised that I thought there was something fundamentally missing from the way that Tudor music was being performed in public. It seemed to me that it was always for this select few cognoscenti, when actually it needed to get to a much wider public. And that’s basically been our mission over the years, to get a wider public and perform the music in a way that reflects what we’re singing about. Nobody knows Latin any more, of course (most people don’t even know what the words of the Mass mean), so somehow we’ve had to inject what the words mean into the way we perform, and really interpret the music. Over the years I’ve also realised that, yes, this is great music, and actually a lot of it can be interpreted in many different ways by different people. We performers all have our way, we all probably think we’re right, but we all attract our own public, which is great.’

The Sixteen certainly haven’t had much problem attracting a public in recent years. Their appearances with Simon Russell Beale in the BBC television series Sacred Music (2008 and 2010) have quite possibly made them the most famous choir in Britain. ‘Thank you, BBC!’ laughs Christophers. ‘And the great thing is that we didn’t have to dumb down. We could introduce people to this music by going so far in explaining it but without going totally over their heads. It’s amazing the number of people who responded to that. Young people, too, especially when we turned up in university cities. I remember once, when we were in Lancaster, a lad came up to us who had the Eton Choirbook box-set and said he listened to a bit of it every week. That’s great, and he wasn’t even a music student!’

But it’s the Choral Pilgrimages – projects which each year since 2000 have toured a single well-honed programme to cathedrals and major churches throughout the country – that have proved the choir’s most effective calling card. And with CDs from The Sixteen’s own label Coro on sale at all the concerts, it’s a tidy financial model too. Christophers describes it as a concept that emerged as a way of rationalising a period in the 1990s when the choir was almost chaotically busy in the recording studio. ‘Everyone thought we were stark staring mad at first, but actually here we are 19 years on still doing it at about 30 venues up and down the country. We’re never going to go away from our policy of bringing this music to a wider public. You know, I’m not going to put in the Allegri Miserere every year to ensure bums on seats. And with the public that comes, it’s always the music they were scared of that they go away talking about at the end. Last year it was Britten’s Sacred and Profane; if there wasn’t a group like us doing it, thousands of people would never hear it.’

He’s right, as I witnessed for myself at a Choral Pilgrimage concert in York Minster in 2013 when the piece in question was the Miserere (2009) by Sir James MacMillan. ‘Everyone needed to calm down afterwards, it was so emotionally moving,’ says Christophers. MacMillan is a composer with whom The Sixteen have forged a special bond, and in 2001 he became the first composer to be commissioned by them. ‘I wanted something for our next Choral Pilgrimage programme to go with some Robert Carver, and I phoned him up and said it would be wonderful to have a contemporary composition on the same text (‘O bone Jesu’), and he said that would be fabulous because it means so much to Scottish Catholics (which I never knew!). We’d done music by other well-known composers who when they start writing vocally put high Cs for sopranos pianissimo and low Cs fortissimo, and I really didn’t want that – with our lot we’d have been calling for an ambulance! So we talked about that, and in this piece there’s a phenomenal crescendo which happens towards the end and feels as if it starts in the basses on a bottom C, when in fact it doesn’t – it starts on a G or something; and it feels as if the sopranos finish on a top C, when actually they finish on an A – and it’s thrilling, so exciting. He really got it. And when he came to the rehearsals, in that moment we felt, “We commissioned you because we like your music and we’re going to perform it to the best of our ability,” and he thought, “Wow, they’re really committed to making this as good as they can.” Which sounds sort of obvious, but when you talk to so many composers about their premieres, they often feel short-changed.’

The intensely moving Stabat mater (2015) – commissioned for The Sixteen by the Catholic philanthropist John Studzinski’s Genesis Foundation – followed in 2016, and for the ensemble’s 40th anniversary they have another MacMillan work to showcase in their 2019 Choral Pilgrimage. Entitled O virgo prudentissima (2017) and already available on their recent ‘Star of Heaven’ CD (Edward Breen described it in these pages – 1/19 – as ‘sumptuous’ and ‘statuesque’), it is based on a fragment by Robert Wilkinson from the Eton Choirbook. Christophers simply calls it ‘fantastic’ and enthuses about its innovative and demanding choral textures: ‘He’s taken us to a lot of new terrains. Just like with Britten’s music you think, “Will we be able to do this?” But in the end you can, and it’s really, really rewarding.’

This year also sees the choir receiving a heavy-duty birthday present from MacMillan, again commissioned for The Sixteen by the Genesis Foundation, in the form of a choral symphony to be premiered at the Edinburgh International Festival on August 17. Featuring the combined forces of The Sixteen, their development choir Genesis Sixteen and the Scottish Chamber Orchestra, it sets a Brittenish mix of biblical and poetic texts in Latin, Greek, Hebrew and English. ‘John Studzinski wanted something on the subject of the Holy Spirit, and originally it was going to be an oratorio, but then Jimmy said, “Well, actually, I’d like my fifth symphony to be a choral symphony.”’ Entitled Le grand inconnu, it’s ‘mammoth!’ says Christophers: ‘Whereas in the Stabat mater the string writing was almost a cinematic representation of what was going on at the foot of the Cross, in the symphony the orchestral writing is incredibly vivid and active, everybody stretched to the nth degree of their artistry. The choral writing likewise, with lots of effects. But then there are unaccompanied chunks which are typical Jimmy. The big thing about his music is that because he’s a believer he really gets to the bottom of things – there’s an inner depth and emotion there. Spirituality applies to everybody, of different faiths and no faith, and emotions can’t help but rise. Jimmy’s music does that.’

The Sixteen are not just an a cappella choir, of course, and over the years they have recorded much of the Baroque choral repertoire with their own orchestra. Handel has been a constant presence, and The Sixteen have recently released a new recording of Acis and Galatea (‘I wanted to show off some of our singers as soloists’) and will be performing a staged version of the oratorio Belshazzar at the Grange Festival between June 20 and July 6. ‘I love doing opera. The nature of the beast is that I don’t get much time to do it, but to have the choir involved in it as well is great. The orchestra is a very important part of our work, and they’re bloody good! Coming from the singing world, when I started with period orchestras I was learning constantly from them, and still am. Those players know so much about the instruments and the repertoire, and I feed off it.’

And to round off the celebrations, there’s A New Heaven, a book of interviews with Radio 3 presenter Sara Mohr-Pietsch to be published by Faber & Faber on August 15. ‘Sara is amazing. She really has the ability to make me think about things. I always tend to think things just happen, but she would say to me, “Harry, things don’t just happen, you must have made them happen!” It’s quite therapeutic.’

So, hoping that Sara won’t mind if I take a leaf out of her book, I try the Mohr-Pietsch technique: how has a man of Christophers’s natural humility and apparent lack of authoritarian high-handedness made The Sixteen one of the best choirs in the world? True to form, he initially looks as if the question has never occurred to him. Then: ‘Well, I suppose I’m lucky that I’m doing something I enjoy, working with this wonderful group. And being a singer myself, I know how to push them. I find performance exhilarating, because it’s so spontaneous, and they have to be absolutely committed. I want their faces to be like actors on a stage, and if there are moments when I get at all dictatorial, that’s the moment they stop doing that. I suppose it sounds flippant, but we have a lot of fun performing, and if the fun’s taken out of it, the results are not going to be the same any more.’

The Sixteen’s Choral Pilgrimage 2019 is now under way, and runs until October 26. They give the world premiere of James MacMillan’s Symphony No 5 at the Edinburgh Festival on August 17, the US premiere of his Stabat mater at Lincoln Center, New York, on November 7, and perform Handel’s Messiah at Westminster Cathedral on December 5. The Sixteen’s 40th Anniversary Collection is out in May on CORO; visit https://thesixteen.com