The latex lips play the trumpet

The physics of brass instruments are not well understood, said Dr Murray Campbell, in the University of Edinburgh's Acoustics Group.

"You'd be surprised how little is known about the relationship between what a brass player does with their lips, what the instrument tries to do and the note that actually comes out," he said.

Murray Campbell plays the trumpet

"We can't offer advice to players and teachers yet, but we hope we might be able to in future," he told BBC News Online. "And we're all performing brass players with a keen personal interest in the work."

Trembling lips

Murray Campbell talks about the artificial lips

Woodwind instruments have a vibrating reed in the mouthpiece but in brass instruments a player's lips are the oscillating device that creates the note. The lips force vibrating air through a funnel-shaped mouthpiece into the resonant tube of the instrument.

But the relationship between the shape of the lips and the note produced by the instrument is complex. Changes in lip vibration do not produce proportional changes in the note. "It's strongly non-linear," said Dr Campbell, whose work is published in New Scientist magazine.

The problem is that analysing how the lips and instrument interact requires lips to be held in a fixed position for up to 10 minutes. No human player can maintain this, which is where the artificial lips come in.

Plastic teeth

These were created by French physicists Joël Gilbert and Jean-François Petiot using two thin latex tubes. The tubes are filled with water so they mimic the density and flexibility of our own lips.

And as air is blown through them, it flows through a perforated plastic plate that simulates the effect of teeth. The tension in the "lips" can also be adjusted to mimic different playing styles.

Dr Campbell has constructed a new version of the French system in Edinburgh for a series of tests.

He told BBC News Online: "There is one very interesting feature which is not yet fully understood called "lipping". Just by adjusting the way that you set your lips on a trumpet's mouthpiece, as well as the tension of the lips and the way you blow, you can change the note quite a lot.