Sing it in Latin, say it with choirs and, deo volente, you will have a bigger hit than you ever believed possible. That's what the populace wants these days. Here endeth the first lesson in selling CDs.
Wander into any record shop these days, and you'll notice a lot of Latin. Canto Gregoriano - music with soothing overtones of the hereafter, from the mellifluous monks of Santo Domingo de Silos. Adiemus: Songs of Sanctuary - an equally soothing but more ethnic mix, from the man who wrote the Renault Clio theme. Officium - in which the Nordic saxophonist Jan Garbarek improvises across the Hilliard Ensemble in choral works from the 14th and 15th centuries. At the Piccadilly branch of Tower Records, that particular album has been in the Top 20 every week for the past two years. But what's this new apparition on the shelves?

You've probably heard of it; you may well have heard it too. Agnus Dei - a devotional compilation sung by the choir of New College, Oxford - has just leapt to No 1 in the classical charts, and 68th position in the pops. A successful operation for Warner Classics - and a coup for their young marketing manager, Dickon Stainer. But seldom was a coup so meticulously planned. And, since this is how our culture is now routinely formed, it's worth a closer look.

"To be honest," says Stainer, "the idea arose out of our seeing four records doing very well over the last three years: Gorecki's Third Symphony, Canto Gregoriano, Adiemus, and the Hilliard Ensemble's Officium. They sold 1.5 million copies in the UK alone - and, apart from the Gorecki, they weren't on our label. So I decided to analyse their appeal."

Six "focus groups" - all buyers of at least one of the above top-sellers - were interviewed in depth. First finding: they were not habitual buyers of classical records, they simply wanted music to relax to, and Mike Oldfield's Tubular Bells did just as well. Second finding: they wanted something "spiritual", but they didn't want "in-your-face churchiness".

Stainer then played them three tapes he had specially recorded: a chorale by Allegri, an anthem by Gorecki, and a choral version of Samuel Barber's Adagio (better known as the soundtrack for Platoon). Thumbs up all round. He then showed them some covers he thought might appeal - a stained-glass window, a Byzantine angel, and a Highgate Cemetery angel - but got a rebuff. "They didn't want that sort of imagery shoved down their throats."

But he also had up his sleeve a photo of a pillar in Salisbury Cathedral, almost abstract, suggesting a wheatsheaf: this was fine. And they wanted it in "soothing" pale blue, so pale blue it would be. Early on in the discussion, he says, the phrase "inner harmony" surfaced as being of key importance. And people loved Latin. "It had a resonance for them, even though they didn't understand it. I doubt very much whether most of our customers know they are buying something called Lamb of God." (The chief inspector for schools should take heart: there are votes in putting Latin back on the curriculum.)

Anyway, there we have it: Agnus Dei: music of inner harmony, including pieces by Palestrina, Mozart, Mendelssohn and the inevitable John Tavener, all packaged up in colours normally associated with intimate female toiletry. "Warner Classics Concocts the Tranquilliser that Needs No Prescription" shouts the press release: since music's curative powers are once more being recognised, this is the perfect note to strike.

Choosing the choir was easy, adds Stainer, who is himself a former Ely Cathedral chorister. "Choirs go up and down like football teams," he says, "and New College are the best at the moment. To be honest" - he uses that phrase a lot - "I was a bit worried at first about how they'd respond to such a mass-marketing concept." But clearly he needn't have worried - it will swell their coffers (though not as much as Warners', with anticipated sales of 100,000 copies this year).

"Some people might say this was a cynical exercise," Stainer admits. "But it's not. We believe in it, and we love the music." So what's his next wheeze? "For obvious reasons I can't tell you - but we're looking at folk songs, everything from Oh Waly Waly to Shenandoah, given in beautiful new arrangements. The sort of thing people who go to leafy heritage concerts like to listen to - Middle England. There are incredible riches there." Quite so.

As we speak, his name begins to ring a bell. And sure enough, he turns out to be the great-great-grandson of Sir John Stainer, whose Crucifixion was once the Easter mainstay of every church choir in Britain. To be honest again, Dickon, what would the old boy say about Agnus Dei? "Oh - er - he liked popular music. So I think he would be pleased." Well, perhaps.