Such a humble device and yet in its own way a miracle. What other reference standard is so simple, yet will with reasonable care give years, decades or even centuries of faithful service? It needs no servicing or recalibration, no batteries, can be kept in a coat pocket not a temperature-controlled environment and does not come with a 300-page instruction manual in 27 languages. Dear reader I give you - the tuning-fork.

Construction is simple: a single piece of metal - usually steel - with two prongs¹ of equal length in the shape of an elongated-U, and a handle at the bottom of the U, together somewhat resembling a two-pronged cutlery fork, after which it is named. The prongs may be either circular or rectangular in cross-section. It is activated by gently tapping one of the prongs on a firm but compliant surface, such as your knee, and then holding the end of the handle in firm contact with a resonant surface.

What's It Used For?

The tuning-fork has uses both musical and medical. If you've ever played a stringed instrument such as a violin or an acoustic guitar, you will probably have used one of these forks to tune your instrument. First you get one string tuned correctly - usually the A string on a violin or the top E string on a guitar - then you tune the other strings relative to this one. Tuning-forks may be used by choirmasters to get their choir all singing at the same pitch.

Even if you've never seen or used a tuning-fork for musical purposes, you may have had one used on you by your doctor to test for sensorineural deafness or peripheral nerve damage.

Good Vibrations

Very soon after being struck, the tuning-fork vibrations stabilise to produce an almost pure tone with very few harmonic additions. The prongs of the fork vibrate in their plane, bending toward and away from each other as though they were trying to clap. This motion is translated, via the join at the bottom of the U, into an up and down vibration in the handle of the fork. The vibration and hence the sound from the tuning-fork is sustained for quite some time.

The direct air-borne sound output from a tuning-fork is very weak unless held close to the ear. This results from the fact that the prongs are bending in opposite directions: when the left-hand prong is bending to its right, the right-hand prong is bending to its left, and vice versa. The sound waves from the two prongs are therefore in anti-phase, almost cancelling each other out. A solution to this problem is achieved if the end of the handle is touched onto a sounding board, such as a table, your skull or even your teeth, whereon the vibrations of the fork are amplified considerably!

In manufacture, tuning-forks are made very slightly over-length - hence slightly flat in pitch - and then fine-tuned by filing or grinding them to the required frequency. Their finish is usually chrome-plated or blued-steel. They are stamped with their musical scale note and its frequency in hertz.

The Shore Family

Although we cannot be certain of the fact, invention of the tuning-fork is usually attributed² to a man called John Shore (c 1662-1752) in 1711. He was one of a family triumvirate of noted trumpet players. All three would hold the post of sergeant-trumpeter to the royal court: John Shore succeeded his uncle William, who in turn had succeeded John's father Matthias. They were all among the band of musicians that accompanied King William III to Holland in 1691.

John Shore had been a trumpeter-in-ordinary from 1688 onwards in the service of Kings James II and William III, Queen Anne, and Kings George I and II. In 1711, the time he is said to have invented the tuning-fork, he was the sergeant-trumpeter to the court of George I. A supremely gifted player - John and William were considered to be the finest English trumpet players of their day - it was for him that Handel, court composer to the king, wrote many of the intricate trumpet parts in his music. Henry Purcell almost certainly had them in mind for the virtuoso parts in his works.

It was not his trumpet, however, that provided the incentive for Shore's invention, but rather his wish for an improvement on the pitch-pipes used to tune the lute which he also played³ - he was appointed lutenist at the Chapel Royal in 1715 in the service of the newly-crowned King George II.

The tuning-fork was described in A New Musical Grammar by William Tans'ur, published in 1746.

All Together Now

Prior to the invention of the tuning-fork, musical pitch was something of a local custom, rather like time before the coming of the railways. Although band members could agree a common pitch between themselves, the pitch adopted varied considerably from country to country in Europe, between towns and regions in the same country and even between bands in the same town, a headache for musicians who played in different bands, as many did. Although some instruments, such as stringed ones, are easily re-tuned to match the band in which they are playing, others such as the oboe and the bassoon are not; they can only be played at the pitch at which they are made. This necessitated many wind players in particular having to possess more than one instrument, an unwanted expense.

Although Shore's tuning-fork provided a portable standard which brought a degree of uniformity to the art of musical instrument tuning, it did not mean that henceforth all musicians tuned to the same pitch. For various reasons - some musical and some not - a common pitch tuning standard was not achieved until 1939, and even today there are small variations in absolute pitch between the world's major orchestras.

The Pitch of the Baroque Orchestra

Shore gave one of his tuning-forks to the composer George Frideric Handel; it still exists today⁴. It is pitched at C₅ = 512Hz, equivalent to A₄ = 422.5Hz. Present-day standard concert pitch is around A₄ = 440Hz, which gives an indication of the relatively lower pitch in use in Handel's time compared with that today. Remember also that the use of equal temperament (except on fretted instruments) did not become standard in France and Germany until the mid-1750s, and a century later in England. Prior to that, mean-tone temperament was the norm for keyboard instruments. It was not possible to measure the frequency of a given note accurately until the mid-1830s.

A Range of Forks

Today a whole range of tuning-forks may be purchased, the choice usually depending upon which instrument is to be tuned. Most common are those at A440, C523.3 and E329.6, although other notes, such as A415 used by period-instrument bands for baroque music, are also found. Complete sets comprising a series of 13 forks, one for each note of the chromatic scale of the octave C₄ to C₅, are available for specialists.