Mike Gluyas is one of a small number of more-or-less serious academics who run a joyous and thoroughly unprofitable sideline in entertaining people with rip-roaring demonstrations of simple scientific principles. These shows, often punctuated by flames, explosions, gunfire and other hair-raising (and probably reportable) incidents, have entertained generations of children, students and ordinary folk ever since Michael Faraday took time off from inventing electromagnetism to amaze young Victorians at the Royal Institution of London.

Not as dangerous-looking as many such lectures, Gluyas's show - called Musical Squares - is devoted to the gentle science of sound, a topic that has been all but squeezed out of undergraduate physics syllabuses.

I intercepted Gluyas and his co-starring wife, Wendy, on one of their frequent dashes across country between shows. Their creaking Vauxhall Astra estate was loaded with more than six hundredweight of tape recorders, amplifiers, speakers, cables and all the other paraphernalia of the travelling showman-scientist. I wanted to know what induced otherwise sensible people to leave the cosy seclusion of their laboratories to seek fame, if not fortune, on the open road. The answer, as I suspected, was fun.

Musical Squares began in 1967, shortly after Gluyas had taken up a lecturing post in physics at Salford University. 'My expertise was in electronics, and I was always interested in hi-fi equipment and sound recording. I suppose I wanted an excuse to get out and play with my toys in public, and doing this in schools seemed a very good idea.' Gluyas and his colleague Mervyn Black, whose parallel epic on the thrills of liquid nitrogen, entitled Say it with Frozen Flowers, started a local fashion which, at its height, had dozens of Salford dons going out into the world to bring science to children.

The name Musical Squares probably once had something to do with musical chairs but now, as Gluyas freely admits, it is sufficiently vague to ensure that his audience can never know what to expect. 'When people go along to listen to a lecture I hope we surprise them a little bit. What we do is more of a happening than a lecture.'

In fact the show is tightly scripted, weaving sound effects and cartoons with demonstrations of waves, resonance, animal noises, speech, music and much else. 'We reach a very wide audience because we make it clear that no previous knowledge whatsoever of the subject is required.'

Wendy Gluyas stage-manages the audiovisual effects from behind a stack of impressive black boxes. 'It takes two of us to work it because it is really a very fast-flowing business,' says Mike. 'In the course of an hour and ten minutes Wendy gets through nearly 180 slides, about seven or eight audio tapes and CDs as well. 'Most of the electronics is home-made, and manufacturers seem only too willing to lend expensive items for use in the show. And there is not a computer in sight.

In an age of television and video, of Spielberg and computer games, of instant visual gratification, it may be surprising that the traditional lecture is still popular. 'It's almost impossible to compete with the polish and professionalism that can be brought to bear on the television screen. People say, 'Let's video it,' but if you do it turns out to be rather poor television.' Yet Musical Squares regularly packs in the crowds; people will still go out in the evening and sit in a hall to listen to a man talk about science.

Lecturing is an art, and the art is that of theatre, of showmanship, of playing to a sea of living faces. Effortless though it may seem, the classic-lecture demonstration has been scripted, choreographed, rehearsed, honed and polished to near-perfection. Some, like Musical Squares, have been running for decades. 'To do a lecture like that from scratch would take months of preparation. You're seeing something that has evolved over many years.'

And as with any live performance, there is always the risk of something going wrong. The lecture at the British Association meeting in Plymouth last summer was dogged by electrical faults. 'The BBC broadcast a bit of the lecture for its Science Now programme. If they had managed to decipher the mumblings that were going on between Wendy and myself they would never have used it.'

Now a part-time teacher at Salford, Gluyas has more time than ever to devote to Musical Squares. Popular though the show remains, he senses that the long tradition of lecture-demonstration faces an uncertain future. 'There's really quite a small band of us giving these lectures and we're all getting older. I don't see many new young people coming in at the bottom, carting equipment around and doing lectures. There's a young lad at Liverpool who does a lecture called the Mathematics of Juggling - he goes around juggling on a unicycle and talks about the mathematics - but apart from him we just have not seen any new people.'

In the new, fierce world of enterprise-universities, brave is the young scientist who would take time off to entertain and inspire children when he or she could be churning out the research papers, winning the contracts and notching up the performance indicators that will keep their name out of the relegation zone.

So who is to broadcast the stomachs of the future generations?