We’ve got plenty of xylophones for children to hit, so we don’t turn anyone away for being too young,” says Arnold Myers, honorary curator of Edinburgh University’s Collection of Historical Instruments. “But we tend to leave out the history aspect with younger groups and and just let them gain an impression of the variety of musical instruments.” Older children usually come because they’re doing a project on the history of the instrument they play: “nine times out of ten, it’s the flute”.

Founded in the 1850s by the university’s then Professor of Music, John Donaldson, the collection, situated in Edinburgh’s old Town, is the oldest purpose-built museum of musical instruments in the world. The original collection consisted of just a handful of old or unusual instruments that had been acquired by John Donaldson himself, but now the museum has more than 1,000 stringed, woodwind, brass, percussion and folk instruments, dating from 1500 to the present day.

As the museum has no paid staff, let alone an education officer, school parties are shown around by knowledgeable volunteers or by Mr Myers himself, who teaches the history of instruments at postgraduate level. Generally speaking, the exhibits remain safely behind glass, though if older musical children come alone or with parents they are sometimes allowed to handle them.

“It’s best if children have a bit of an interest before they come, although they do tend to get interested just by being here,” says Mr Myers, who has compiled a quiz sheet for children to fill in as they go round the gallery.

As it’s the history and variety of the instruments that’s interesting, rather than their value, he hates being asked whether the collection has a Stradivarius. “We haven’t got one and I don’t want one,” he states firmly. “They may be worth a lot, but they’re of little historic interest as almost none are in their original state.”

However, the collection includes so many unusual and fascinating exhibits that it is hard to imagine anyone being dissatisfied with it.

One of the most ancient instruments is a 1594 tenor trombone - the only one in Britain. Instruments of this age are seldom played, because they can easily be damaged, but a short piece was performed on it at a historical concert given to mark its own 400th birthday in 1994.

Equally unique is a giant, 16-foot serpent (an instrument later superseded by the ophicleide and the tuba), known as the “Anaconda”. The only known example of a contrabass serpent, it was made in 1840, by two brothers, Joseph and Richard Wood, who played it for 20 years in their local church near Huddersfield and in York Minster.

In addition to historic versions of recorders, violins, clarinets, trumpets and every other non-keyboard instrument that is still played today, there are countless others from bygone eras - lutes, cornets, sackbutts, viols, rebecs, the pocket viol-ins used by dancing masters, crumhorns, hurdy-gurdies, early 10-stringed guitars and much more.

The museum also houses a fine collection of bagpipes, including one dating back to 1793, when there was a much greater variety of pipes: loud outdoor ones, quiet indoor ones and special pipes for dancing.

Entry to the museum is free, but there is a charge for school concerts. If all goes well, the collection will soon occupy a new purpose-built site next door to to the Russell Collection of Early Keyboard Instruments in nearby St Cecilia’s Hall. But more than Pounds 1 million has still to be raised for the project, which will include multi-media displays.

The Russell Collection is also open to school parties, but as its 47 harpsichords, spinets, virginals and clavichords are not protected by showcases, the curator, Dr Grant O’Brien, stresses that school-age visitors should be people “of maturity and discipline”. About half the instruments have been fully restored and are regularly played by serious early keyboard musicians. School parties are normally shown around by the assistant curator, John Raymond, who includes some accomplished demonstrations in his one-hour tour.

The collection’s oldest playing instrument is a 1585 Italian virginal by Bertolotti, while one of its youngest is the first English grand piano, once owned by the Duke of Wellington. As a whole, the collection demonstrates the way early keyboard instruments developed and changed until they were finally overtaken by the piano in the 1760s.

Many are as interesting for their exquisitely decorated cases and the pastoral scenes painted inside their lids as for musical curiosities such as divided accidental keys. We may consider E flat and D sharp to be the same note, but many early virginals and harpsichords differentiated between them.

Like the Collection of Historical Instruments, the Russell Collection owes its existence to the vision of a single collector, Raymond Russell, whose family presented his collection to the university after his death in 1964, to fulfil his lifelong dream of establishing a “live” museum of restored keyboard instruments.

The Royal College of Music in South Kensington in London also has its own Museum of Instruments, based on a collection donated to the college by Sir George Donaldson when the conservatoire first opened in 1894. With keyboard and non-keyboard instruments housed together in one fine purpose-built gallery, the collection includes 600 exhibits from 1480 to the present day, including 100 Asian and African instruments.

Fewer of the keyboard instruments are in working condition than in the Edinburgh collection, as the Royal College has a policy of preserving exhibits in their original state. But demonstrations are given on copies and children can also hear recordings of the wind, string, and other instruments.

Curator Elizabeth Wells is happy to tailor school visits to specific projects on, say, the harpsichord or piano. “We usually begin by asking the children what they all play, and then focus on bits of the exhibition that will appeal to them. It all depends on the age-group.”

Among the museum’s many treasures are a 1480 German clavicytherium (the world’s earliest surviving string keyboard instrument), a 1531 Italian harpsichord, a 1794 clavichord on which Haydn composed his Creation, a 1750 spinet reputed to have belonged to Handel and a guitar that belonged to Rossini.

Upstairs in the separate Portrait and Performance Department is Britain’s most comprehensive collection of musical prints and portraits. It includes Thomas Hardy’s famous portrait of Haydn, a painting of Weber on the last day of his life and a signed 1817 engraving of Beethoven, on which the proud owner wrote, after meeting him, “very like”.

Recent plans to rehouse the Museum of Instruments and the Department of Portraits, both now bursting at the seams, in the former Royal College of organists next to the Albert Hall, have been shelved for lack of money. The idea, which must now remain a dream, was to create a National Museum of Music.

Edinburgh University Collection of Musical Instruments, Reid Concert Hall, Bristo Square, Teviot Place, Edinburgh EH8 9AG. Open Wednesdays 3-5pm, Saturdays 10am-1pm. Admission free. For conducted tours, write to the curator, Arnold Myers * Russell Collection of Early Keyboard Instruments, St Cecilia’s Hall, Niddry Street, Cowgate, Edinburgh EH1 1LJ. Open Wednesdays 2-5pm, Saturdays 10.30-12.30. For conducted tours, write to the curator, Grant O’Brien * Royal College of Music Museum of Instruments, Prince Consort Road, South Kensington, London SW7 2BS. open Wednesdays, 2-4.30pm. Parties by appointment with the curator, Elizabeth Wells.

Tel: 0171 589 4346 * To visit the Department of Portraits and Performance History, contact Oliver Davis, tel: 0171 591 4