The Finest Violins May Have 'Evolved' by Mistake

To understand a violin is to understand the physics of sound. And, given that the physics of sound look an awful lot like the physics of wave phenomena in general, to understand the violin is to understand some of the deepest physics in our world.

So it shouldn't be very surprising to learn that MIT researchers—funded by the US Navy—are diligently at work measuring and ​analyzing the acoustic properties of Cremonese-era violins, instruments hailing from what's considered to be the "golden era" of violin-making that can fetch millions of dollars apiece. The results of these efforts, a quantitative characterization of the acoustic power efficiency of centuries-old wooden boxes, are to be published in the Proceedings of the Royal Society: A.

The conclusion is unexpected. Most likely, the key improvements in violin design made during the era came as accidents. The instrument's development can then be looked at as an evolutionary process: some irregularity or slip in the process of carving out the body of a violin just worked better, and so it persisted. A mistake (mutation) becomes a feature.

The weird thing is that violins have always pretty much looked like violins and a cheap plywood knockoff bought off eBay tomorrow will have the same basic characteristics, and even most of the same fine characteristics, as a Stradivarius. The enormous differences in sound quality come in the superfine (relatively) subtleties of an instrument, and this is where things get interesting.

The finest violin bow and the finest stretched silver violin strings can only do so much. The vibrations of the string itself are tiny and near-silent, the result of minute slips between the string and the horsehair of a bow. It's only when those vibrations travel downward through the instrument's bridge and propagate through its wooden body do we get the full, rich sound of the thing, which is the point. (An electric violin isn't so much a violin as it is a set of strings.) And wood is an excellent conductor of acoustic energy, much better than air, and so what we wind up hearing is really a deep impression of every resonating nuance and cut leftover from the violin-maker's hands and blade.

It's a bit mystical.

Or it's mystical in that way that physics can feel mystical, particularly when it comes to periodic, resonant phenomena, which, in addition to making music sound deep and nice, has been known to destroy hig​hway bridges and (nearly) enti​re shopping malls. A resonant frequency is a hell of a thing, and there remain many things just about violins and resonance that are still poorly ​understood, which has to do with the large number of oscillating structures—strings, bridge, top plates, posts, ribs, fingerboard, etc.—all coupled together, with the result being the tone we actually hear.

The MIT physicists tracked two violin features in particular: the length of the violin's "f-holes" and the thickness of its backplate. The f-holes, the curved openings on either side of the violin's frontside, were found to be a key driver of power efficiency, as slight elongations can result in big increases in sound. Violins with thicker backplates also boosted output efficiency. So, the instrument's evolution through the studied period shows a steady increase in f-hole elongation and a steady increase in backplate thickness, but the question becomes whether or not the changes were even intentional.

Without direct evidence of violin-maker intent, it's not so easy to answer. So the physicists, over the course of a seven-year investigation beginning with 10th century lutes and ending with relatively modern violins, tried to determine whether or not the changes could be explained by an evolutionary model. Could a violin "just happen"?

"We found that if you try to replicate a sound hole exactly from the last one you made, you'll always have a little error," said Nicholas Makris, a professor of engineering at MIT, in a statement. "You're cutting with a knife into thin wood and you can't get it perfectly, and the error we report is about two percent … always within what would have happened if it was an evolutionary change, accidentally from random fluctuations."

Ascribing genius to accident isn't a very satisfying perspective, but handmaking a wooden instrument 800 years ago was all about accidents. Or accidents and listening.

"People had to be listening, and had to be picking things that were more efficient, and were making good selection of what instrument to replicate," Makris said. "Whether they understood, 'Oh, we need to make [the sound hole] more slender,' we can't say. But they definitely knew what was a better instrument to replicate."