Mirror, mirror on the wall, who has the purest voice of all, boys or girls? STEPHEN LEWIS investigates.

Boy chorister: la-la-la-la-la. Girl chorister: la-la-la-la-la. Can you hear the difference. No? Join the club.

New research by a York academic has shown that ordinary people simply can't distinguish the sound of a boys' choir from a girls' choir.

Professor David Howard, an electronics engineer at York University with a special interest in acoustics and the sound of the human singing voice, played recordings of a girls' and boys' choir to about 200 ordinary listeners - and found that they weren't able to tell the difference. Choirgirls, it seems, really are every bit as angelic as choirboys.

It's a finding that on the face of it threatens to throw 500 years of choral tradition out of the window - and one that the great church and cathedral choirs are not going to accept without a fight.

To be fair, Prof Howard does accept that there may well be a slight difference in the quality of girls' and boys' solo voices. Every individual is different, he points out, and the quality of the voice depends partly on the age of the singer. But generally it is accepted that choirboys (remember Aled Jones?) produce a more flute-like, pure, penetrating voice than girls, who have a slightly more breathy and husky quality.

Those differences may be noticeable at a certain pitch range - roughly the upper treble range, Prof Howard says.

But in a choir, he says, the individual voices blend - and this subtle difference in quality is lost, to all but the most trained of ears. To claim girls' choirs are not as good as boys' choirs, therefore, is "primarily sexist", the professor says. "It's got nothing to do with music."

It is not a new argument. Boys have been singing in church and cathedral choirs for 500 years or so - but most cathedrals have only introduced girls choirs since 1991, when the parents of a girl who was turned down by the choir of Salisbury Cathedral took the case to the European court.

Most cathedrals now have girls choirs - including York Minster, which introduced one in the mid-1990s. But for the most part girls' and boys' choirs are kept entirely separate, singing together only on very rare occasions. And apart from anything else, points out the professor, keeping two separate choirs is an expensive waste of money.

So should the choirs be combined, and girls be allowed to sing alongside boys? No, insists Philip Moore, organist and master of music at York Minster.

It is something about which people will argue endlessly, he admits. But he insists there is a difference in the sound produced by a girls' choir and a boys' choir. "Generally speaking, especially as the boys mature, the collective sound they produce is stronger than the girls in the lower register," he says.

"The girls have a slightly different sound. I think the sound that our girls produce is a completely valid musical sound, but I feel it would be quite wrong to say goodbye to the all-male choir. It is something that we don't want to throw away because it does have a uniqueness about it."

Martin Dryer, the Evening Press classical music critic and lecturer on English Church Music who is himself a former choirboy, agrees.

The top line as sung by a boys' choir - especially one in which the boys are reaching an age where their voices will soon break - has a clarity and cutting edge that a girls' choir can't quite match, he says.

He would not like to see the merging of boys' and girls' choirs - partly because he fears it could lead to a shortage in the number of boys who mature into adult choristers.

"Generally speaking, boys don't much like at that age being mixed up with girls," he says. "They regard it as a sissy activity."

Some choirs are already having difficulty attracting enough boys, he points out - and in the long term there is a danger that there may not be enough boys going on to become adult counter tenors, tenors or even bass singers with our great church choirs.

It is not a debate that is likely to end with one new scientific study. Whatever Professor Howard's findings, many will continue to feel there is something special about the pure sound of a choirboy's soaring voice - even if it remains difficult to isolate precisely what it is.

Evening Press arts writer and former choirboy Charles Hutchinson is one who feels that way. He has nothing against girls' choirs, he stresses. "But it is my belief that there is no purer sound than the individual voice of a choirboy singing Once In Royal David's City in a candlelit church at the start of a carol service."

Updated: 12:12 Wednesday, September 10, 2003