Peter Phillips has spent 40 years perfecting the Tallis Scholar’s distinctive rich polyphonic purr to run like a well oiled machine.

Many things about the Tallis Scholars make them one of the world’s great professional choirs, but it’s essentially the sound: a smooth, rich, Rolls-Royce purr that Peter Phillips, their director, has spent forty years perfecting.

And he knows the worth of what he’s done – as audiences will hear when the Scholars sweep into Hampstead Garden Suburb for the Proms at St Jude’s next week.

“We’re the Berlin Philharmonic of the choral world,” he says, in terms that read immodestly but have a certain charm when spoken in his donnish way. With a degree of mischief.

“People take it for granted now”, he says, “but it took some doing. From the start I wanted something strong but agile, capable of wide dynamic range and able to be loud without distortion.

“Any choir can sing softly, but sing loud and the blend disintegrates, voices stick out, vibrato widens, and the tuning goes.

“That the Tallis Scholars actually sing in tune has always been one of our selling points.

“It may not seem like a big deal, but when we started in 1973 it was rare for a group like ours, singing the repertoire we did, to stay in tune.

“I like to think we made a significant contribution to cleaning things up”.

In 1973 Phillips was still an Oxford undergraduate, in love with renaissance polyphony - the music of Palestrina, Tallis, Byrd and Taverner – and spellbound by the way the Clerks of Oxenford and one or two like-minded choirs were resurrecting it, with scholarship and “authenticity”.

Those were the nursery years of what we now call period performance.

Emma Kirkby was its vocal pin-up. Oxbridge was in thrall to people playing shawms in cheesecloth skirts and sandals.

To be new and cutting-edge was to be old and digging into music’s past.

And out of all this came the Tallis Scholars, started by a group of friends who barely knew what they were doing.

“We were 19 and exploring music for the fun of it”, says Phillips. “There was no money, just a sense of pioneering and a shared enthusiasm for obscure composers nobody had heard of”.

Fortunately, there turned out to be a market for obscurity.

Through four decades the Scholars have amassed over 2000 concerts, 60 discs, with countless radio and TV broadcasts.

They’ve performed in every continent except Antarctica - an understandable omission, although one that will be remedied in two years’ time when they go out and premiere a specially commissioned piece by Nico Muhly – to an audience of scientists and penguins.

“It began as a joke”, says Phillips, “because somebody had noticed the Antarctic was about the only place on earth we hadn’t sung, and I thought: OK, let’s see what we can do about that.

“There’s going to be a TV documentary.”

By comparison, St Jude’s will be an easy gig and warmer – with a programme that’s effectively a Tallis Scholars calling-card.

Allegri, Byrd and Tallis are the period-performed heart of it, alongside modern music by John Tavener (with whom the Scholars had a close relationship) and Arvo Part (featured composer on their latest CD), and the premiere of a Miserere setting by a young British composer, Alexander Campkin.

“It’s all very Us, I think”, says Phillips as we take tea in the garden of his house in one of Islington’s more fashionable squares. “It wasn’t fashionable when we moved here”, he protests.

“We led the way”. A lifelong habit.

The Tallis Scholars at St Jude’s, Hampstead Garden Suburb, Friday 1st July, 7.45pm. promsatstjudes.org.uk