There are about seven hundred Stradivarius violins still intact from the 17th century, and they are among the most sought-after instruments in the world (3). Most, if not all, of the greatest violinists of modern times believe that there is something in the Cremonese violins that provides superior tonal quality to all other violins. Skilled violinists can even distinguish between different qualities in the sound produced by individual Stradivarius violins. The challenge for scientists is to characterize such differences by physical measurements. In practice, it is extremely difficult to distinguish between a Stradivarius instrument and a modern copy on the basis of measured responses because the ear is a supreme detection device and the brain is a far more sophisticated analyzer of complex sounds than any system yet developed to assess musical quality. There have been many theories as to why Stradivarius violins produce such legendary brilliance and resonance, none providing a conclusive answer.
To understand the factors that affect the quality of sound produced by violins, the functioning of the violin must be understood. First of all, sound is produced by drawing a bow across one or more of the four stretched strings, but the strings themselves produce almost no sound. The energy from the vibrating string is transferred to the sound box, which is the main body of the violin. The bridge, which supports the strings, acts as a mechanical transformer; it converts the transverse forces of the strings into the vibrational modes of the sound box (4). The bridge itself also has resonant modes, playing a role in the overall tone. The front plate of the violin is expertly carved with f-holes which boost the sound output at low frequencies, through the Helmholtz air resonance. The Helmholtz air resonance describes the action of the air bouncing backwards and forwards through the f-holes (1). Then, front and back plates are skillfully carved to get the right degree of arching and variation in thickness. Even the tiniest changes in the thickness of the plates and the smallest variations in the properties of the wood will significantly affect the specific resonance in the frequency range (1).
There are many theories as to the "secret" of Stradivarius violins. Of course what was obviously first explored was the exact size of the violins and ratio of the parts of the violin to each other. It was proposed that perhaps the magic lay in some perfect ratio of measurements in the pieces of the violin, but instrument makers have disassembled their violins, calibrated every dimension of the pieces to within the hundredth of an inch, and replicated the measurements perfectly in new instruments, but failed to duplicate the Stradivarius magic (2). Another factor to consider is that almost all Cremonese instruments underwent extensive restoration and improvement in the 19th century. For example, in the 19th century, both the bass bar and the sound post were made bigger to strengthen the instrument and increase the sound output. The bass bar is glued underneath the top plate to stop energy being dissipated into acoustically inefficient higher-order modes. The sound post is a solid rod wedged between the back and front plates which causes the bridge to rock, making the plates vibrate with larger amplitude, producing a stronger sound (1).
Some tests suggest that early Italian makers, such as Stradivari, may have tuned the resonant modes of the individual front and back plates to exact musical intervals (1). They would be identified by the traditional flexing and tapping of the plates, in essence, the violin maker's brain providing the interpretative computing power to perform nodal analysis. This would be consistent with the prevailing Renaissance view of perfection, which was measure in terms of numbers and exact ratios. Unfortunately, there is no historical evidence to support this case, and physicists have used lab equipment to analyze the vibrational patterns of Cremonese violin front and back plates and had craftsmen carve new plates that faithfully reproduce the patterns, yet still the extraordinary and brilliant tone of Stradivari's violins is missing (2). Also, top players regularly return their instruments to violin makers to optimize the sound by moving the sound post and adjusting the bridge, showing that there is no unique set of vibrational characteristics for any particular instrument, even a Stradivarius (1).
A claim had been made by one of the last famed Cremonese violin makers, Joannes Baptista Guadagnini, that Stradivari's secret laid in using wood that had been dry-aged, with no extra treatment (3). The problem was that in Venice, from 1700 until 1720, when Stradivari produced his most prized and valued violins, wood supplies were tightly controlled by government authorities. People would have been thrown in jail for simply walking out and cutting wood from the forests. Authorized woodcutters felled trees and dumped the longs into rivers where they were carried downstream to the capital. By the time violin makers had access to the wood, it had been sitting in water for weeks or even months at a time (2). When wood shavings from Cremonese instruments were examined, residue of bacteria and fungi showed up, just as you'd expect in wood which had been sitting in water. This suggests that perhaps Guadagnini was deliberately misleading people so that nobody could replicate the great masters.
One of the most widely known theories is that the secret lies in a special kind of varnish used. Scholars from Cambridge University used electron microscopy to identify many of the ingredients of the varnish itself and the materials used to smooth the surface before the varnish is applied (1). They concluded that most could have easily been bought from the pharmacist shop next to Stradivari's workshop and that there is no convincing evidence to support the idea of a secret formula. Joseph Nagyvary has a slightly different take on the varnish issue. He claims that the local lumberman and the local apothecary simply happened to supply Stradivari with the ideal wood and perfect varnish; the production of his magnificent and extraordinary instruments was just a lucky accident (3).
The secret to producing such amazing tonal quality, he claims lies in the varnish. Nagyvary proposes the idea that the insect-repelling mixture of "salt of gems" (which are finely crushed crystals) and borax that the Cremonese violin makers used as varnish is what fossilized the wood to a perfect pitch (3). He believed that the violin makers treated their wood with mineral solutions, which is not a far-fetched idea, as the alchemy books of the time had plenty of recipes for mineral-rich wood preservatives used by furniture makers to protect chairs and tables against damage from insects and general rot. Salt of gems was commonly used as well to add stiffness to the wood and make the finish glitter. Nagyvary's idea is that the accidental chemical reaction of phosphates and wood lifted Stradivarius's violins to a whole new level.
The finish of the most pristine of the surviving Stradivarius instruments has a brittle, almost glassy look. If Stradivari's varnish contained sugar or a polysaccharide, the molecules would have attached to one another and to the wood, stiffening it so it could vibrate more efficiently (4). Fruit-tree extracts were widely used in wood varnishes as well, and Nagyvary claims that the pectin creates polymers which continue to add to the superior brilliance of the Stradivarius tonal quality (3). Unfortunately, ultraviolet photography has revealed that many fine-sounding Italian violins have lost almost all their original varnish. These violins were recoated during the 19th century or later (1). Therefore, the composition of the varnish may have had little to do with the overall superior tonal quality of the Stradivarius violins.
Another important finding by Nagyvary is that violins acknowledged to be great by expert listeners all look similar on the sound analyzer. He found that the sound pattern almost exactly reproduces that of a human voice (2). He built violins to match the spectrogram tests of the Stradivarius violins, results registering between 4,000 and 6,000 kHz, the zone where the human ear is the most sensitive. Shunsuke Sato, a top violinist, played both a Stradivarius violin and Nagyvary's replica as a test. Though Nagyvary's violin exhibits an uncommon brilliance and resonance, the Stradivarius violin sounded much warmer and even the untrained ear could hear a distinct difference (3).
A new theory which has emerged attributes the climate of the time period to the uncommonly amazing sound of the Stradivarius violins. A tree-ring dating expert, from the University of Texas, and a climatologist, from Columbia University, claim that the wood used by Stradivari had developed special acoustic properties as it was growing because of a "Little Ice Age" (4). They propose the idea that an extended period of long winters and cool summers gripped Europe from the mid-1400s until the mid-1800s. The peak coldest point of this ice age was during a seventy year period from 1645 until 1715, known as the Maunder Minimum. This change in climate affected wood density, yielding uncommonly dense Alpine spruce for Stradivari, creating superior tonal quality. Stradivari was born the year before the Maunder Minimum began and produced his most prized and valued instruments from 1700 until 1720, right at the end of the period. These experts write that the narrow tree rings which personify the Maunder Minimum in Europe played a role in the enhanced sound quality of instruments produced by the Cremona violinmakers and that the narrow tree rings would not only strengthen the violin but would also increase the wood's density (4).
Overall, science has not provided any conclusive answer on the existence or otherwise of any measurable property that would set Stradivarius violins apart from the finest violins made by skilled craftsmen today. However, the really top soloists and the violin dealers remain convinced by the legend of the Stradivarius violins. Perhaps this is due to certain snobbery on the part of the violinists, attempting to set themselves aside as elite. Perhaps it is the dealers who do not want people questioning whether simply the name of Stradivari alone is worth a million dollars. Certainly, the secret of the Stradivarius violins is elusive. I would find it interesting, in light of this new study on the climate of the 17th century in Italy, to have scientists grow a crop of trees in controlled climates to produce exceptionally narrow rings, then attempt to recreate the magic of the Cremonese violins. This may be the real key to unlocking Stradivari's secret. Personally, I find it intriguing that science cannot find an answer to the brilliance of the Stradivarius violin's sound. Highly trained individuals can detect the difference between a Stradivarius and a new modern copy, however good the copy may be. Skilled individuals can detect the difference between the sounds of an Italian Cremonese sound and those with a more French tone. Experts can even tell apart an individual Stradivarius from another Stradivarius. Yet do not know how to characterize such properties in meaningful physical terms.
I mirror this article because I felt it was good and I could gather some comments from my readers and friends. The original link to this article is http://serendip.brynmawr.edu/biology/b103/f03/web3/s1kim.html
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