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AUGUST 19, 2022    

Soul Mate
By James N. McKean

Copyright held by author all rights reserved.
Everyone has a particular nightmare, that recurring dream that wakes you up in a cold sweat in the early hours of the morning. According to a psychologist I know, running in place while being pursued – not being able to get away – is the most common; standing naked in a crowd is a close runner-up. Musicians who play a stringed instrument have a different devil to plague them in the small hours of the night (at least as they reveal them to me): They are about to go onstage. The house is sold out (those with particularly active imaginations add that there are stage seats). They discover they need to change a string. They take off the old one, and the soundpost falls down. They are standing there, listening to the post rattle around in the violin, desperately trying to figure out what to do – get a coat hanger? a piece of string? a fork? – when the red light goes on and the stagehand appears and tells them they have to go on. That’s the point when they wake up.
But sometimes life can be worse than a nightmare. Ask violinist Chee-Yun; it was a year ago that she was in the middle of the third movement of the Bruch concerto before a full house in Greenwich, Connecticut, when the soundpost in her violin popped out. She did the only thing she could, and the only thing you can do if it ever happens to you: she found another violin to finish the concert. In this case, it was the concert-master’s.
If you’ve ever had the misfortune to play a violin without its soundpost, you realize how vital it is. The French, in fact, call it the ├óme, the word for soul, and it could be said that the post fulfills the same central role in your instrument. Its function is not only acoustic; with the strings tuned up to pitch, the top can collapse if the post is down. By itself, the top is not nearly strong enough to withstand the 40-odd pounds of pressure (close to twice that on cellos) exerted on it by the bridge. It needs reinforcement, which comes on the bass side from the bass bar, a strip of wood that is fitted and glued into the top. On the treble side, the soundpost plays this vital part.
The post itself could not seem more innocuous – a simple spruce dowel that’s merely wedged in place (it's not glued, as most people assume, which is why it occasionally falls down). But getting one to fit correctly is one of the most difficult and exacting tasks in the craft. It was the last thing we learned how to do at violinmaking school, and when I first attempted it I quickly learned why; just getting it through the f-hole without having it fall off the setter takes practice. The soundpost setter is an S-shaped iron tool, as much the hallmark of a violin shop as a stethoscope is of a doctor’s office. It has a sharp point on one end for spearing the post, and a pair of blunt, hooklike knobs at the other for yanking it around. Musicians often ask me where to get one, a question that never ceases to amaze me.
You run as much risk of doing serious damage trying to move your post around as you would if you tried to do a root canal at home. I know that sounds like a professional trying to protect a convenient source of income, but adjusting the post without the proper training and experience is just asking for trouble. Take a quick look at the diagram (top, above) and you can begin to see why.
The ends of the soundpost are cut at a slant to match the tapering of the body. The difference between a post that fits and one that doesn’t can be as little as a shaving. After each cut, the post must be put back in the instrument and checked by looking at it from the lower end, through the tiny hole where the button or endpin is usually seated. And – just to complicate matters – a mirror is the only way to be sure that the other side, which you can’t see from the endhole, also fits. (This is actually a point at which violin making and dentistry do intersect; the mirror I use for this was originally used by my grandfather in his dental practice.)
The danger posed by a post that doesn’t match the taper of the instrument is that it will gouge the inside of the top. The edges of the post are sharp, and if they don’t fit exactly, they can easily dent or tear the top. Spruce, the wood that both the top and the soundpost are made from, is one of the strongest natural materials known, for its weight, but it’s not the toughest. The side grain of spruce, the surface that the post rests against, is very soft and easily dented. On the other hand, the part of the post that meets the top is endgrain, which is very hard. Think about chewing on a pencil and how easy it is to mark it up; your teeth on the cedar pencil have about the same effect as an ill-fitting post on the unprotected wood of the top (or back; over time, an ill-fitting post can even dent maple).
You can also see that if the post is not standing perfectly straight, the sharp edges of even the most well-fitted post could cause damage. Keeping the post perpendicular requires training; I can remember spending endless hours learning to get it just right. The violinist Bronislaw Huberman was well known for adjusting his own post – in fact, he would sometimes switch posts just before going on stage. Whether it improved his performance is debatable, but what it did to his Stradivari isn’t. After Huberman died, the Wurlitzer shop had to put a soundpost patch in the violin’s top to repair the wood destroyed by the incessant replacing and moving of the post.
You can see now how Chee-Yun’s soundpost could have popped free; it didn’t match the taper of her instrument. She plays a Ruggieri violin modeled, as most are, on the Grand Pattern Amati. The back has a particularly pointed arch, which means that the surface the bottom of the post rests on is steeply inclined. Maple, when it is burnished, can be as slick as a piece of glass, and it doesn’t take much adjusting of the post to polish that surface to a fine smoothness. If the post is to stay, it must fit exactly; too much of an angle either way and it won’t hold.
The chances of the post actually popping out are extremely slim. What does happen, not infrequently, is that the post falls down when the string pressure is off the instrument. This can happen when the weather suddenly turns cold and dry – you might open the case and find that the pegs have all come loose. If the post does fall down when the pressure is off, it means that it is too short. But beware of a post that is too long; they are sometimes installed in an effort to boost the instrument’s power and edge. Over time, they can cause serious damage, distorting the arching or even opening a crack. Also beware the common misconception that instruments need soundposts of different lengths for summer and winter. I’ve never found this to be true, even for instruments that need different bridges. In fact, I can’t recall ever having to do a seasonal adjustment of a soundpost, let alone fitting a new one.
Adjusting brings us to the other function of the soundpost. Aside from its purely structural use in holding up the top, it plays a role in the acoustics of your instrument. When you draw the bow, the sound waves travel through the bridge to the body, which acts as an amplifier. The violin is often compared to the human voice, and with good reason; the violin is the instrument that comes closest to producing as many overtones as you hear when you’re listening to a singer. Most of these are produced by the way the string vibrates, but the rest come from the body of the instrument itself. The wood not only vibrates, it also moves: as the bow pulls the string, the bridge rocks, which moves the top up and down. The soundpost acts like a plunger, transmitting this movement to the back. Where the post sits relative to the bridge will directly affect the way the sound waves from the string and the motion of the bridge are transmitted to the back.
This, then, is where adjusting comes in. It's a process steeped in mystery; anyone who has spent any time around violins knows that there is a cult of the adjustment, a sort of acoustic juju with which some people are reputed to be endowed. It does take a certain touch, and some are better at it than others, but it isn't much of a mystery. This diagram shows the position of the post as viewed from above. The soundpost doesn't sit directly under the bridge foot; it is slightly behind it, and to the inside. Both of these distances are changed when the post is adjusted. By moving the post in or out -- to the left or right on the diagram -- the rocking motion of the bridge is affected. Moving it out makes it stiffer (much as spreading your feet steadies your stance), and more of the rocking is thrown to the bassbar, affecting the balance of the sound of the strings. Moving the post closer or further from the entire bridge -- up or down on the diagram -- also changes the amount of time for the sound waves to reach the back, thus affecting the focus or depth of the sound. As slight as it is, this phase delay in time between the resonance of the top and then the back contributes to the complexity of the overtones as the instrument is played.
By moving the post in these two directions, the instrument's response and tone quality can be fine-tuned. An experienced adjuster can tell by listening and watching you play what needs to be done. I adjust cellos as much by the vibration I feel in the floor as by what I hear and see. Anything you can put into words will also help, and you shouldn't feel shy about expressing what it is that is troulbing you about the way your instrument is responding. The exact vocabulary isn't important, although there is a lexicon for the adjusting process: "Sluggish," "nasal," "covered," "too dark," "metallic," "harsh," "bright," "raw" -- these are some of the terms most commonly used.
The most important thing to remember about the adjustment of your instrument is that it can never be optimal all the time. Any halfway decent violin is built to be responsive, to the weather and the seasons as much as to the pressure of the bow. As an amplifier, it amplifies your mood as well as the sound of the strings. If you're having an off day, the chances are excellent that your instrument will, too. What you have to avoid is the temptation to have the instrument adjusted for every variation you feel or hear in its repsonse. It is all too easy to become fixated on the soundpost as the cause and cure of all troubles (just remember Huberman). The French have it right: the soundpost is like the soul, best nourished by being the least troubled.

     James N. McKean has been making, restoring, and dealing in fine violins in New York City since 1977, when he graduated from The Violinmaking School of America. His articles regularly appear in Strings Magazine, for which he is a Corresponding Editor. He has served in a number of positions on the Board of the American Federation of Violin and Bow Makers, including President.

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