Britain's choirboys sing a simple, and glorious, song unto the Lord

''People visit us,'' says Anthony Crossland, organist and choirmaster at Wells Cathedral, Somerset, ''and are amazed to find the music and singing are done by live people.

Mr. Crossland, a genial Englishman wearing a comfortable brown suit this morning, has just arrived in the choir's rehearsal room to put the 16 Wells choristers through their paces. In termtime, each morning starts with 11/2 hours of practice - and in the evenings there is still further practice followed by evensong in the cathedral. The choristers are boys of assorted sizes, 9 to 13 years old. They form up eight-a-side, left and right of the piano. Christopher Brayne, assistant organist, sits at the keyboard, and Mr. Crossland stands at its prow. The choristers' mascot, a teddy bear, lolls on the piano lid. He is named Bubwith, after one of the medieval bishops of Wells, and is dressed accordingly.

There is a shuffling of feet on the bare floorboards - and then suddenly the air is filled with astonishing song - ethereal, fluting, exalted singing to ''rinse and wring the ear,'' in the poet Hopkins's words; an extraordinary mixture of vocal innocence and sophistication.

Above the choirboys' heads on the wall is a poster that makes its own whimsical comment on the proceedings. It shows a number of birds on a bough, with one of them chirruping: ''Sing a simple song unto the Lord!''

The actual singers make it sound simple enough, standing at their music stands like small professionals: ''My soul doth magnify the Lord!'' they sing, and ''Glory be to the Father, and to the Son. . . .''

''Yes, that's fine,'' smiles the choirmaster avuncularly. ''Not bad, not bad at all.''

Slowly, with scrupulous measure, they launch into the ''Nunc Dimittis'': ''Lord, now lettest Thou Thy servant depart in peace, according to Thy Word. . . .''

And so the rehearsing continues, Mr. Crossland clapping his hands now and then to intersperse such comments as ''Let's hear a clear 'd' on Lord,'' or ''Ah-eee! That sounds like a lot of football supporters!'' By a process he later described to me as ''trial and error'' he builds up the sound he wants: a matter of intuition, one gathers, rather than conscious technique or aesthetics.

''Hallelujah!'' - they raise the roof - ''HALLELUJAH!'' There's no doubt about it - they're live people all right.

Today's boy choristers are heirs to a long tradition which is peculiarly English. There are still all sorts of choirs in churches up and down Britain. The Royal School of Church Music has affiliated to it some 6,500 of them. They are active in small rural parishes as well as large, important, high-vaulted city cathedrals. But everyone I spoke to agreed on one thing: The finest choir-singing in Britain is produced now, just as it was centuries ago, by the cathedral choirs of men and boys.

There is in 1984 vigorous support for the continuation of this tradition in the Church of England. The attitude of a woman staff-member of the Anglican Cathedral in Liverpool (a city that supports two cathedral choirs, the other being Roman Catholic) was characteristic. When I asked her if there were women or girls in the choir, she shuddered. ''Oooh, no'' she said emphatically, shocked at the very notion.

Mr. Crossland at Wells is a keen advocate of the tradition too. He admits with a smile that it is a ''male chauvinist preserve'' and today's expertise does make it possible to train some girls to ''sound like boys.'' But he still believes that the choirboy, his special schooling, and his naturally unique sound are well worth preserving simply on the grounds that they are such an old tradition.

What, I wondered, is it that makes the choirboy sound so unmistakable?

Mr. Crossland describes the singing produced by girls of chorister age as ''a more colored sound - a certain amount of controlled vibrato. If carried to an extreme, this can become nasty. In that sense, boys' voices tend to be thought of as a purer sound. . . . Hundreds of years ago they thought this sound to be more suitable for the impersonal, religious impression they wanted to convey.''

I also discussed this with Terry Gore, recently conductor of the Vienna Festival Ballet and himself a chorister in the '60s at Canterbury. He told me that ''girls seem to sing from the heart,'' while ''the whole point about a choirboy's voice is that it's not sung with the vocal chords; it's like an organ pipe. So you actually flute the notes. You're not actually singing the notes. You're using your voice as an instrument.''

There are of course differences between boys' choirs. As a complete contrast to British cathedral choirs Mr. Gore cites the famous Vienna Boys' Choir. ''They belt everything! It's a very continental sound. Very hard-hitting.'' The ideal when Mr. Gore was a chorister was the so-called ''English sound,'' quite distinct from anything heard on the Continent.

Mr. Crossland, however, relegates this to the past. ''The 'English sound' used to be a sort of 'hoot,' '' he says.

''A hoot?''

''The beauty of the tone was sought without the clarity of the words,'' he explains. Following that tendency there was a swing overboard in Britain toward the very nasal sound of the Continent. ''Now, I think there's a tendency to compromise between the two.''

But he also points out that the special qualities of men's and boy's choirs become increasingly a unique British institution as one sees ''these traditions gradually extinguished on the Continent.''

They are very old traditions indeed.

Mr. Crossland gave me a copy of a document written by one of the bishops at Wells, Thomas of Beckinton. It is headed ''The Rules for Choristers, 1460.'' Apart from emphasizing that boys fulfilling the ''office of chorister'' must have both suitable voices and suitable dispositions, and that at table they must ''cut their bread or break it decently, not gnaw it with their teeth or tear it with their nails,'' it also lays down requirements about wearing ''clean surplices'' in the choir, and ''goodly copes in good repair reaching down to the ankles in accordance with the ancient usage of the church.'' It is that final phrase which illustrates just what is meant by ''traditions.'' Bishop Beckinton, 524 years ago, could refer to the proper dress for choirboys at Wells as ''an ancient usage!''

In 1984 the perpetuation of such traditions is encountering certain obstacles in common with the churches themselves. Clergymen are being greatly overworked, says the dean of St. Paul's Cathedral in a recent article. The Times of London interviews a short-staffed vicar who, with the help of one curate, has to care for the parishioners of no fewer than 10 rural parishes. And as for choir schools, they are not immune from the recession. Media reports have revealed in some cases a drop in applications for places. Parents, though assisted by grants and scholarships, are finding it harder even to afford the fees at the (usually private) choir schools.

''A number of small choir schools have gone under in recent years,'' Mr. Crossland confirms. But one school publicized on television, which had only three applicants for voice trials the previous year, this year had 25. At Wells, if the numbers applying have decreased somewhat, the quality seems maintained if not improved. And financially this school has been greatly helped by an unexpected and large legacy ''for the cathedral music.''

''Also,'' Mr. Crossland points out, ''some currently flourishing choir schools are not comparatively very many years old. The Abbey School at Tewkesbury (attached to the splendid 12th-century abbey) was, for instance, only begun 11 years ago by Miles Amherst, whose 'dominant interest in life is church music.' ''

Apparently going strong, this new school forms a link with choristers who sang at Tewkesbury before the Dissolution of the Monasteries in Henry VII's time (late 15th, early 16th centuries). As at other choir schools, the choristers are numerically only a small and hard-working sector, though obviously special. Music is taught to a particularly high standard throughout the school.

However hard the times are, the Choir Schools Association map of Britain still shows choirs schools dotted thickly across the country, from Exeter to Durham, from Canterbury to Hereford, from York to Winchester. They can also be found in Edinburgh, Llandaff (Wales), and Dubin.

One result of threats to the very existence of church choir traditions in Britain is, as Christopher Brayne points out, that they have become ''more competitive, in a friendly way.'' They make records. They give recitals. They go abroad on concert tours. They are familiar with television cameras and studios. They are assessed by music critics. They can even develop charisma: The choirs of King's and St. John's Colleges at Cambridge have become so popular that queues of eager visitors can form outside their chapels before evensong. St. Paul's choristers made their mark at the royal wedding in 1982. The Pope's visit brought others, such as Canterbury and Liverpool, onto television screens last year. And the sound of choirboys is heard on BBC radio twice every week when evensong from one cathedral or other is broadcast. The popularity of this became evident when the BBC threatened to stop doing it a few years ago. There was an outcry.

As for Wells choristers, they are becoming adept at travel: Germany and Holland one year, and in 1983 Canada and Seattle, Wash.

Inevitably, perhaps, such publicity brings a certain self-consciousness to choirs and choristers. Some see a danger of ''performance'' and ''theater'' - the desire even to entertain - creeping in to downgrade the original intention for the singing to be integral to the worship of the church: for ''the glory of God.''

Anthony Crossland, however, feels that a rigorous musical standard does not have to be incompatible with the basic, though reticently emphasized, religious purpose of choristers. ''We do tend to remind them from time to time of why they are here,'' he says quietly. At the same time the schools are at pains to point out that choirboys are very normal small boys, good at games, academically above standard and not at all prissy. One chorister - Christian Bembridge, 10, in the choir at Gloucester - agrees in the form of a poem for the 1983 edition of ''The Choir Schools Review'':

''Cassock red, surplice white,

Mouths wide open, singing right.

Can you guess? Can you not?

We look like angels, but we're not!''

Philip Peabody, now master of the Junior School at Wells, recalls choristers used to be allowed to take books into the services to read during the sermon!

On the other hand, there is no laxity in terms of musical standards today. Mr. Crossland says that choristers ''do feel themselves, I think quite rightly, to be an elite.'' And he adds, ''One is aiming at a fairly high professional standard. I always tell them it's comparable . . . to a professional symphony orchestra. But your 'players' are only 9-, 10-, 11-, and 12-year-olds. I don't make any allowances! I say to them, 'You might be performing now to a higher standard than you'll ever do in your lives again.' There's a great sense of achievement.''

These days choristers generally ''retire'' at 13, when their voices break. Terry Gore went on, back in the '60s, until he was 15. And the other day in Edinburgh I met William Minay, a lifetime organist, choirmaster, teacher, and (firstly) choirster. Noe an octogenarian, he told me with a mischievous twinkle in his eye that his voice didn't break until he was 36, in 1940! Perhaps he simply didn't want to retire.

Richard Morgan, 13, had mixed feelings about the end of his career as a chorister at Peterborough Cathedral. Writing in the aforementioned review a few months after he "shut the door of the Song School for the last time," that close-knit society. I miss the grandeur of our services and concerts, and being able to brag about our broadcasts. I loved the chorister's way of life.

"But," (he concludes, all the same) "it's great to be free!"

At the other end of the same piece of rope is a rhyme by Fraser Dingley, 9, chorister at the Cathedral School, Llandaff, Wales:

"I'm a new boy in the choir, A bit bemused and small, But the music I am singing Makes me feel so very tall.

Presumably that is also just how they used to feel in 1460. How to find them

An annually updated Directory of Choral Services at Cathedrals, Collegiate Churches, and Chapels is even published by the English Tourist Board (4, Grosvenor Gardens, London SW1W ODU, Tel.: 01-730-3400). Since choristers, like all schoolchildren, have vacations, the summer, particularyly August, tends to be a blank month for anyone planning a 'chorister tour,' The best times are the quieter tourist seasons of spring and fall.