Does your voice sound different when you sing in the bath? Dr Brian White, biology teacher and singer, once took the question beyond mere speculation. He recorded his voice as he lay up to his neck in water in the bath and analysed the tape with a spectrograph.

Dr White - he received a doctorate for his work on the science of the voice, of which the bath experiment was atiny part - is a part-time singer of professional quality and serious intent. Whereas singing may be an enjoyable relaxation for most of us, for Brian White, it is also a demanding art that calls for care and respect. He has to nurture his voice through diligent practice and constant visits to teachers. “It’s a hobby,” he says, “but a professional one.”

He has an impressive bass-baritone voice - even, warm, with a hint of steel. The authoritative sound he produces is prized by choral societies, which hire him to perform in oratorios such as Handel’s Messiah and Haydn’s Creation. He also takes part in operatic concerts and performs solo recitals of the standard male vocal repertoire, from Benjamin Britten to Schubert and Schumann.

Recently, he has been diversifying, with regular programmes of Gershwin, Cole Porter, Irving Berlin and - carefully selected - Elvis Presley numbers. He performs these at Pizza Express in Maidstone, Kent, which has a reputation for its programmes of jazz and popular music. “I’d always longed to croon like Bing Crosby,” he says. “And in recent years I’ve had the opportunity.”

But in spite of this professionalism, Dr White has never aspired to a full-time singing career. For one thing there is simply too little work to go round. “I’d be unable to support my family,” he explains. In any case, he says, he likes his teaching job too much. “I love my subject - I’m a hands-on biologist. ”

He also likes his school - Invicta Grammar in Maidstone, Kent - where he has taught for 23 years. Although a head of department, he has not sought to join senior management, explaining that “it would have meant going down the admin path, and that wouldn’t have suited me. I love the academic challenge - I’ve just finished an MA in curriculum development.” He makes a contribution to school music, too, helping with A-level and school concerts.

The attention he pays to his art has its own effect on his classroom work. Like most serious singers, for example, he pays careful attention to his posture, using the Alexander technique - “You should feel as if you are suspended from the ceiling - head forward and up, abdomen in, chest raised. ” Many singers, he says, fall into bad postural habits. Correct posture, though, “looks strong. You want to dominate theaudience.”

And, of course, standing well and looking confident does a teacher no harm. “In school, I’m in posture all the time - it becomes automatic.”

He also does exercises whenever possible. “Today I was doing abdominal exercises while I was teaching. You’ve got to - you can’t be unfit and a singer.”

He is also careful to use proper vocal technique in class, trying not to shout. “If I want the class to pay attention, I’ll lower my voice. I’ve got a loud voice. But it does get tired by the end of the day.”

One hazard, though, has disappeared from Invicta’s classrooms. “I’m glad we’ve got rid of chalkboards. The dust was very damaging,” Dr White says.

Looking after the voice, and ensuring it is always available for performance also means having regular flu jabs and keeping away from coughs and sneezes. “I avoid crowded places, so I’ll travel first-class on the train. I don’t go into pubs, where there are bugs and smoke.”

For the same reason, colleagues with colds find him suddenly unsociable. “After all,” he explains, “I might be teaching on Wednesday and singing in the Creation on Saturday. I’ve yet to miss a big concert.”

All musicians need to find time for regular practice. A singer who teaches, though, carries the extra problem of having to exercise an instrument that has been in use all day. “In fact,” Brian White explains, “there’s no point in practising in the evening if the voice is tired - it just makes things worse.”

But there are other kinds of study - learning scores, going over difficult passages at less than full voice, memorising the text. Remembering words, in fact, is his biggest challenge. “It’s what worries me most. I’ve thought a lot about memory and learning. In the end you have to find the way that suits you.”

What Brian White does is write out by hand the words he has to learn. “Writing makes them sink in. The music, though, I learn photographically - I see the page. Many musicians do that.”

Careful practising and memorising, says Brian White, are the basics of good performance. “You can’t go in front of an audience and not be well prepared. ” Even when he comperes a school concert, for example, he prepares carefully. Many non-performers, he believes, fail to understand this and consequently do badly. “They develop a fear of standing up.”

The mental and physical links between classroom teaching and serious singing are striking. Careful use of the voice; confident posture; basic fitness; attention to the techniques of learning; a realisation that performance (on stage or in class) rests on good preparation - these principles are common to both.

Properly applied, they may well turn a relatively introspective person into a confident performer - a teacher, say, who is unruffled at the prospect of taking assembly. Brian White in private, for example, is rather different from the Brian White who stands up to sing at Pizza Express. He lives a quiet suburban life with his wife, daughters and son - all amateur musicians. He insists, “I’m a loner. I’m always in my study. I never watch TV. I hate parties and my work is my relaxation. I’m the opposite to what people would expect. ”

So what makes a quiet family man with a deep interest in academic study stand up in a formal suit in front of hundreds of people who have paid money to hear him? “If you’re a singer you’ve got to sing - you’ve got to be up there. ”