By James N. McKean

Ah, the romance of the violin. Over the centuries, through the good times and even more the cataclysms that have shaken the world, a violin (provided it survives intact) gathers a past, accruing stories—some even true—until it acquires an almost semi-mystical glow. A lot of that is due to hard use and polishing, of course, but over time the violin comes alive, with a character and voice all its own. It takes craft to play it, and craft to make it, but beyond all that lies the art of the violin.

Nothing exemplifies that leap from craft to art more than the bass bar, because it goes to the very heart of the sound of your instrument. It takes the highest level of skill and training to fit it properly, but when it comes to shaping it, there are no numbers or templates to go by; it’s all in the fingertips.

It’s nearly invisible—except for a slight glimpse of it through the bass f-hole—and without the bass bar the top would collapse. A violin top is less than three millimeters thick; a cello top, not much more. And yet when the strings are brought up to their full pitch, the bridge exerts more than 35 pounds of pressure straight down on the center of the top (and more than twice that for a cello).

History of the Bass Bar

Under the treble foot of the bridge, the soundpost supports the top, transferring the weight to the back. Under the other foot, the bass bar carries the weight, distributing it along the length of the top. The bass bars I fit and shape are significantly more robust than those found in violins from the Baroque period and earlier. Those were shorter and lower; the plain gut strings in use at the time had significantly lower tension, resulting in much less pressure on the top.

At the beginning of the 18th century, at the very height of the Baroque period, the demands on musicians began to change. As music became more of a public event, the performance spaces grew larger, along with the size of the orchestra. The repertory, too, began to include concertos. And then, as the Classical style began to emerge, the balance of the orchestra began to change, with an increased emphasis on brass.

String players needed more—more power, more agility, more everything.  Right around 1700 a method was developed to wind gut strings with metal, a breakthrough that allowed a dramatic increase in tension while reducing the gauge of the string. The result: more power and a quicker response. String lengths on cellos could also be shortened, allowing new models to be developed that could accommodate the demand for more virtuosic playing and solo music.

Gradually, strings became available that were made of pure metal—either just a wire, as with the violin E-string, or metal wound on metal. To increase power, the makers began to set the necks longer, and at an angle. Makers also started increasing the string length and making the angle of the strings over the bridge more acute to greatly increase the tension. Lengthening the neck also made it possible to play higher on the stave without shifting.

All of this—the strings combined with setup—increased the power of the instrument, but at the same time dramatically increased the weight on the top. The soundposts became thicker, and bass bars much more substantial. Violin shops had to retrofit older instruments—which, at this point, included pretty much anything made prior to the late-18th century—with new bass bars and, more often than not, neck grafts.

The increase in weight also meant using a slightly different shape for the bar itself—one that is fuller in the center, before tapering at the ends. The bass bar plays a dual role: It has to support the top, and it also distributes the vibrations to the rest of the top. To do this, it has to let the top flex. Fitting the bar is perhaps the most precise step in making an instrument; it has to fit perfectly, along its entire length. The top, made of spruce, is very flexible; even though the bar is also made of spruce, if it is not perfectly fit, its edges can damage the top.

Setting and Shaping a Bass Bar

I use studs tack-glued in the top to ensure the bass bar sits exactly where I want it in relation to the bridge foot. It’s a millimeter or so in from the outside of the foot, but that “or so” can make a material difference in the response and the balance of the sound, because it will affect the rocking of the bridge when you play. There are a number of factors to take into consideration; the stiffness of every top is different, depending on the character of the wood itself, the setting of the f-holes, the shape of the arch, and the varnish.

The studs also ensure that the bar is in exactly the place where I fit it. This is even harder than it appears, with the complex curves of the top, because the bar is fit with tension. I leave a slight gap at the ends, so that when the bar is glued in, the center of the top is lifted slightly. That way the top stays level when it settles back down under the weight of the strings. I have to be able to look out the window as I roll the bar back and forth and not feel the slightest bump; only then is the bar fit well enough to glue.

That’s the craft. That’s like playing scales and études. Shaping the bar is like turning eight pages of notes into the Chaconne: It’s where the art comes in. There really are no numbers to go by—the highest point in the center can vary by over a millimeter, depending on all those same factors that went into placing it. But it’s the way I shape it between the center and the ends that is the real art to the bass bar. It’s all a matter of feel—intuition, shaped by experience.

I use a small plane, slowly reducing the bar, roughing in the taper, flexing it, feeling the balance of stiffness and give; taking more and more, one shaving at a time, until I reach the point where the plane hesitates. And that’s when I know it’s done: when I feel that one more stroke will be one too far. How to explain it? I can’t, which is why it’s an art.

There’s also no way of knowing if you’re right. Could you have taken more, moved the bar out a half-millimeter, used slightly more tension in fitting it, found a piece of spruce with a tighter grain? Perhaps. But you’ll never know. You can take all the measurements in the world, compile data your entire life. But just as each player who will put a bow to the finished instrument is unique, so is each instrument, and so is each bass bar. In the end, it’s a mystery, and that’s what makes it so intriguing and compelling. That’s the romance.

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