Many other theories have been put forward to account for the Stradivarius secret. The most popular for well over a century has been that the varnish had some sort of "magic" composition. The main function of the varnish is to protect the instrument from dirt and to stop it absorbing moisture from the player's hands. The varnish also imparts great aesthetic value to the instrument, with its translucent coating highlighting the beautiful grain structure of the wood below.
However, historical research has shown that the varnish is no different to that used by many furniture makers when Stradivari was alive. Claire Barlow and co-workers at Cambridge University, for example, have used electron microscopy to identify many of the important ingredients of the varnish itself, and the materials that are used to smooth the surface before the varnish is applied. It turns out that most could easily have been bought from the pharmacist shop next to Stradivari's workshop. Apart from the possibility that the varnish was contaminated with the wings of passing insects and debris from the workshop floor, there is no convincing evidence to support the idea of a secret formula!
Indeed, ultraviolet photography has revealed that many fine-sounding Italian violins have lost almost all their original varnish, and were recoated during the 19th century or later. The composition of the varnish is therefore unlikely to be the long-lost secret, although too much varnish would certainly increase the damping and therefore sully the tone.
Other researchers, meanwhile, have claimed that Stradivari's secret was to soak the wood in water, to leach out supposedly harmful chemicals, before it was seasoned. Although this would be consistent with the idea that the masts and oars of recently sunken Venetian war galleys might have been used to make violins, the scientific and historical evidence to support this view is unconvincing.
Over the last 150 years, physicists have made considerable progress in understanding the way the violin works. In the 19th century the "modernized" Stradivarius violin emerged with an "enhanced" tone as a result of scientifically guided "improvements" by the leading violin restorers of the day. However, Stradivari would be amazed to find that the modern musical world credits him with such a secret. After all, how could he possibly have had the clairvoyance to foresee that his instruments would be extensively modified in the 19th century to produce the kind of sound we value so highly today? Indeed, those sounds would have been totally alien to the musical tastes of his time!
Science has not provided any convincing evidence for the existence or otherwise of any measurable property that would set the Cremonese instruments apart from the finest violins made by skilled craftsman today. Indeed, some leading soloists do occasionally play on modern instruments. However, the really top soloists - and, not surprisingly, violin dealers, who have a vested interest in maintaining the Cremonese legend of intrinsic superiority - remain utterly unconvinced.
Maybe there is an essential aspect of violin quality that we are still failing to recognize. Many violinists say they can distinguish an instrument with a fine "Italian Cremonese sound" from one with, say, a more "French" tone, such as my Vuillaume violin. But we still do not know how to characterize such properties in meaningful physical terms.
