By Christopher Jacoby

When choosing an instrument, players are often taken in by romantic details—the color and texture of the varnish, fancy pegs, and tailpiece carving—the bells and whistles. I’ve watched many a client enter a room of violins and already know which one they love the most, drawn to it as if by pheromones. But it’s useful to look beneath these details, to the bones of an instrument, beneath the paint and jewelry—the wood used to build it.

When making instruments, my greatest asset can be my greatest frustration: The materials are natural, and the properties of trees can change from meter to meter when the logs are split up.

Modern exploration of space-age materials—carbon fiber and resin hybrids used in place of spruce and tight-grained maple—has led to interesting results, but nothing as pleasing the ear as good old-fashioned felled trees.
Investing in the stability and predictable response from a carbon-fiber cello makes sense for those traveling often, or working and playing in tropical  humidity.

But for the deep, rich growl of a well-made wooden cello—you just can’t beat the real thing in the concert hall.
So a piece of tonewood, lovingly chosen, sealed, and stacked for a decade, can reveal ugly knots and sap pockets when the violin maker finally takes it down and saws it up. You can’t predict what the wood has in store for you when you’re thumbing through stacks of it for sale, but you can educate yourself to judge its tonal potential without a spectrometer. It’s exciting to dream of the chandelier-shaking instruments you’ll build, but you have to be willing to adjust your plans, or abandon a back or top sometimes, too.

Learn the Specs

When looking at wood for instruments, how does a violin maker make decisions about the materials and method? Let’s define some telling characteristics first.

The grain is the number of winters the tree lived through before it was felled, each darker line representing a period of slower growth, when the tree pulled all its precious sap down under the ground and let the wind and snow strip off its leaves. A wide space between the grain lines indicates fat, lush summers, and as the tree grows bigger and bigger, from the center of its heartwood out, these generally increase in width, as the tree commands more canopy and more root system to process water and sunlight into girth. On most two-piece instrument tops and backs, you can see the winter grains are super tight—close together—at the center joint, and then widen steadily out into the flowing curves of the bouts. If the grain runs vertically, from neck heel to chin rest, this means the piece of wood was quarter-sawn. If the grain is more of a topographical map, with islands and contour lines in swirls, this means the piece of wood was slab-cut.

Quarter-sawn wood for instruments has always been the traditional choice. Imagine a round chunk of a tree’s trunk, sitting on your kitchen table like a tall birthday cake. You have a chainsaw cake knife, and can choose to cut the pieces for your guests a few ways. Quarter-sawn slices come out like a normal piece of cake, widest out at the bark, and cut in to the center and pulled out like a tall triangular prism. When this piece of cake is dried, you cut it in half again and joint the two wide parts from the bark together.

Or you can take your chainsaw cake knife and just cut down the round cake from one side to the other, slab after slab like making parallel tomato slices. This is slab cut.

Traditionally, quarter-sawn wood is considered more stable for instruments, as the tendency to warp and change shape is curbed by long sections of straight grain. But slab wood can make fantastic instruments, and there is some evidence that a warmer, richer sound is achieved by choosing slab.

Next is the best part—the figure. Figure, chatoyance, flame—all refer to the fantastic optical properties of some special pieces of wood. Fiddlers call it “tiger maple,” and I’ve heard some folks call it “lively,” or “fiddleback.” Figure is a genetic anomaly, apparently. It doesn’t seem to benefit the trees, but it surely benefits those of us looking for beautiful materials. If a tree has figure, its offspring, through acorn, seed, or cutting, will carry the genes to produce figure, and that’s that. Every tree species seems to have the capacity to produce figured wood, and the effects of the figure can run wild, from quilted, rippling figure like tropical storms, to the suggestive “bearclaw” figure of evergreens, to the sharp, clean stripes that slash across the ribs and backs of fine instruments.

Fleck is an aspect of figure, and refers to the smaller, prismatic lateral bits crossing grain. I’ve found it more commonly on quarter-sawn wood, and it can appear during the varnishing process on fine pieces of spruce, adding subtle dimension and depth to an otherwise plain top.

Density is a physical characteristic of materials that tells you just how tightly the molecules it’s made of are packed in. Multiply the measured dimensions of the hunk of wood by its weight and you get a number that indicates how dense it is on a usable scale. Stiffness is a measurement of a piece of wood’s resistance to changing its shape due to outside influence. Imagine testing how far bamboo will bend versus a willow switch.

Traditionally, stiffer wood with a lower density is ideal for instruments. It’s light yet stable, and this combination seems to produce a loud sound that projects well.

Knowing the characteristics of the wood lets the luthier make good decisions about how it should be used. I prefer earmarking wood with certain characteristics for certain models, years ahead of time. You always want fantastic figure, of course! Nothing beats a finished viola with figure that looks a foot deep from the front row. But if I have a piece of maple denser and stiffer than my ideal specs, I might choose it to be made into a late-model Stradivari violin. This model has flatter, taut arches that can translate to real power if one chooses slightly denser, stiffer wood, so that the arch needn’t be so round and strong.

The process of violin making is one of removing wild cards from your hand—you need to plan for the finished sound from the first stroke of the gouge, and knowing how to choose your wood for a given project makes the process that much more predictable.