Good vibrations

"We received the plungerphone as a generous donation, after it had been built as a stage prop for a folk musician in Reading, who sadly died before he could use it," said Andy Lamb, the collection's highly-instructive and entertaining assistant curator, who has put together the current exhibition of invented instruments.

"Around the same time we had a young American volunteer working here who arranged a concert at St Cross church including Messiaen's Quartet for the End of Time, which on this occasion featured a theremin. That's an electrophone, where sound is made by electronic wave production," Andy added.

"The person who had made this one, an electronics inventor from Hook Norton called Richard Hellyer, was there. I badgered him into talking about his inventions at one of our lunchtime seminars and to the Friends of the Bate.

"This, together with our newly acquired plungerphone, led to the idea of an exhibition of instruments with no antecedent: the products of a sudden spark of invention. If you look at the development of instruments generally, there's a kind of Darwinian progression from one stage to another, with things getting gradually more and more complex," Andy continued.

Three of Richard Hellyer's inventions are in the exhibition. He has been working in electronics since the 1960s. Now he is trying some ideas that can be used to enable people with certain disabilities to enjoy making music.

Richard is looking for partners to take the development forward - and render his prototypes marketable. His latest device has a microphone into which you can hum a tune that is in your head and the computer will then transcribe it into common notation.

"You can see two of Richard's theremins and his Torchestra here. All of them can be operated by visitors, "Andy said. "This version of the Torchestra is designed for children - you shine a torch beam on one of the pictures and it plays a note on the scale through a loudspeaker. The flashing light hits a light receptor and trips a switch, which produces the musical tone. He has made another one with a more complete keyboard and the potential for 30 or 40 musical tones."

There are also plans for a giant version, which could be used on stage and operated by a searchlight.

The theremins' unearthly sound is activated and controlled by someone moving a hand over optical windows - for instance, one for pitch and one for volume - at varying distances.

"Theremins have a potentially infinite range, over as much as the human ear can pick up and beyond. One of the models we have here has all the guts on display so visitors can see the circuitry, which is built round three small computers," Andy said.

The other is the retro' version, with organ stops in the side for higher and lower octaves, reverberation and tremolo.

The plungerphone, which has a clarinet mouthpiece, was made by John McVey, an instrument maker from Bedfordshire, based on an early German clarinet.

"John has brought in several instruments over the years, including copies of medieval shawm-type instruments which only exist as carvings in churches.

"We are always on the lookout for things our visitors can try out - it is important to us to provide some hands-on experience, particularly for school children. We're not just a sterile gallery," Andy added.

The exhibition also features some older examples of inspired instrument design, such as the development by Theobald Boehm in the 1840s of a new way of keying the flute, and the invention by Adolphe Sax of the saxophone at about the same period.

Sax was influenced in his design by familiarity with a group of military and church band instruments called ophicleides - keyed versions of the old S' shaped serpents.

"They weren't well respected - they were rather fluffy round the edges, with no evenness of tone across the musical spectrum. Sax saw a way to change them by making an acoustically pure shape - more or less straight down with a bell at the end - without having to compromise on the size and position of the tone holes," Andy said.

Another interesting exhibit is the flute prosthetic.

"A man called T.B. Beard, from Weston-super-Mare, injured his hand in World War Two and couldn't play the flute properly, so he had this gadget made, designed so he could hold the flute up using only his thumb," Andy explained. "Something similar has been made for brass players in Northern bands, where the valves can be operated remotely.

"Prosthetic aids for musicians are ancient and very famous. There was a one-handed flautist who was part of the Chatsworth household in the 18th century. He had a specially adapted instrument which they brought down here to show us."

The collection has another invented instrument, which Andy has been involved in restoring.

"It is a glasschord. It works like a vibraphone but with a keyboard driving the hammers that hit glass plates. It is the sort of sound you associate with Papageno in The Magic Flute. They were churned out by the hundreds and not very well made.

"This one had been in someone's attic for decades and was very dirty, so we consolidated the parts that were left and re-attached the leather straps to the hammers. Astonishingly, the glass plates were still intact. It has its original tonal qualities, and it plays, but not to an acceptable orchestral standard."

The current exhibition, with possible additions, will be in place for at least six months.

"While some inventions might seem trivial, and some important, now," said Andy, "down the line you don't know which is going to take the world by storm, or send the spark into someone else's head.

"The plungerphone might seem ludicrous to us at the moment but that doesn't mean there isn't something valuable there, to do with the materials or the design perhaps, or some dual application we haven't thought of."

The Bate Collection of Musical Instruments, Faculty of Music, University of Oxford, St Aldate's, Oxford (next to Christ Church). Admission free. Open Monday-Friday, 2-5pm, and Saturday,10am until noon during University term.