Every GP has one, classical musicians rely on them to maintain the perfect key in concert halls and some believe they can transmit healing powers to cure all manner of ailments. Invented in the 1700s, the tuning fork has a long and important history - and its role endures today with many thousands of the instruments being made every year in Sheffield, home of the sole UK manufacturer.
Ragg Tuning Forks have been forged here since 1841; six years ago, the firm and its employees was bought by Uniplex, a company that supplies medical devices, but the process still remains reassuringly familiar, involving lengths of plain aluminium or steel that are sawn, shaped, ground and polished into precision tools built to last.
And if anyone thinks their daily lives aren't influenced by these little curiosities, they're wrong, says Uniplex's managing director Adriaan Posthuma.
"Speed cameras are calibrated with tuning forks - ours. Radar guns the same. Most of the English-speaking countries in the world buy our tuning forks to calibrate their devices to control the speeding public."
He adds drily: "And no, we won't ever make them anything other than 100 per cent accurate."
The implements were also put to good effect in the era of old-fashioned telephone exchanges. "Every single piece of that equipment was calibrated with a tuning fork. And there's educational establishments as well - they will have tuning forks to demonstrate to pupils not just the effect of sound waves but also how you can move iron filings around and use vibration to create movement."
Uniplex is a member of the Made in Sheffield mark, and its forks are proudly displayed in the Cutlers' Hall. It occupies a 6,000 sq ft site with a factory, offices, warehouses and process rooms on Furnace Hill in an area tied to the city's metalworking heritage. Ragg was bought from another Sheffield outfit, Granton Medical, owned by Peter Kirkby whose mother was a member of the founding family.
"Peter ultimately ended up with the forks company, probably as a result of his mother's gift. His daughter Katy was the one who decided they no longer needed Ragg's in the Granton business, and sold it off."
It remains the 'pre-eminent brand' in the world of musical tuning forks, says Adriaan. "Although they should be correctly called 'tuning forks for musical applications'. They themselves don't make tunes, although they do make notes."
John Shore, a Royal trumpeter who was a favourite of classical composer Handel, is credited with devising the first fork in London in 1711. Prior to this, unreliable wooden pitch pipes were players' only option.
Each instrument, when struck, produces a particular frequency which can be used for the desired purpose such as, say, tuning a piano. Adriaan demonstrates by striking a fork marked C256 - 256Hz being the musical note C, which immediately rings out bright and clear.
"Of course people use tone generators to tune their guitars, which are fine in their immediate environment but once someone goes on to the world stage - arenas, concert halls and the like - everyone has to be tuned to the industry standard," he says. "Ours are guaranteed to be accurate at 22 degrees centigrade. You have to have a reference temperature because the temperature affects the length of the metal."
The firm sells as many as 35,000 forks every year, including boxed sets that equip the buyer with a range of notes.
Special commissions also come in. Most recently, Adriaan was asked to make forks up to two-and-a-half metres long - producing frequencies thought by a customer in France to match 'those needed to rebalance the Earth'. "He's got the belief the planet is out of kilter and he can rebalance it using tuning forks."
World-famous piano maker Steinway has placed orders, as has Sydney Opera House, and the Icelandic singer-songwriter Björk asked for a limited edition run of multi-coloured forks to accompany her 2011 album Biophilia.
"She commissioned us to make 500 sets. You could buy a wooden box, with the relevant tuning forks and a book. The storyline within the book showed you which ones to use for which track. Then you could actually hum along in the appropriate tone key. It was quite an interesting project for all concerned. They were very pretty."
Forks are used to test for nerve damage in patients with diabetes and a particular line - the Gardiner Brown model - is part of the standard kit for a GP to carry out hearing tests. "I would say every doctor in the country will have one. But there lies a problem - they all have one. And they last for a lifetime."
There are areas of growth for Uniplex, however. Practitioners called kinesiologists believe that, when specialist tuning fork sets are applied on and around the body, vibrational shifts occur that correct subtle physical, emotional and energy imbalances. An advocate called Alan Sales designed his own range sold by Ragg that, it is claimed, can help fix back pain and headaches. Meanwhile a client in China once asked for forks tuned to the 'frequency of love' which, it turns out, is 528Hz.
"There are a number of makers of the odd fork but there's probably none that makes such a broad a range as we do," says Adriaan. "Most of the tuning fork makers will make for the musical market, or the medical market, not both."
Forks are machined out of a single piece of metal - nothing is welded on, which ensures better accuracy and holds the note for longer. "You need to have a hard material. The likes of brass, nickel, tin, gold and so on are too soft."
Richard Rawson, one of the original staff who came to Uniplex with Ragg, has been in the trade for well over 40 years. "There are 18 or so different processes to making a fork," he observes, demonstrating how he carefully calibrates each item using a device fitted with electrodes.
At one time materials would have been sourced from local factories, but no longer. "The last batch of aluminium we got came from Russia," says Adriaan. "It's an aerospace alloy that we use and there aren't too many British manufacturers anymore. We do get cold drawn steels from Kiveton."
He is committed to maintaining the strong South Yorkshire connection, though. "The product has actually been improved over the years, with a determination to keep the work in Sheffield."