The bridge in all stringed instruments is a simple, unheralded part that transfers vibrations from the strings to the instrument body. It’s all physics!
There’s an argument in education theory circles that the 21st century emphasis on STEM – preparing students for careers in science, technology, engineering, and math – leaves out something important: the arts. This is why more progressive school systems are now calling it STEAM, with the A representing the visual and performing arts.
That more progressive stance isn’t just about tacking on music or painting classes to coursework in physics, calculus and coding. It’s about integrating all of the above into a relationship, where understanding one might help with understanding another. Better yet, something like studying the violin might help a student gain a better understanding of such things as the Doppler effect, bridge cables, and friction.
Take for examples the violin, viola, cello or stringed bass. All include a small but vital part called the bridge. It’s a simple piece of maple wood, cut in fanciful ways, serving as a lift on the strings to provide their tension. The bridge also raises the strings on a slope that makes the instrument more playable. When the instrument is played, the bridge transmits vibrations of the strings to the body of the instrument, where the sound is then amplified.
Fine stringed instruments require customized bridges that cannot be purchased stock. A violin shop with a reputable in-house luthier who makes or repairs fine cellos, violins and violas, will usually handcraft a fine bridge for a high-end instrument. Though an experienced player can learn to properly place their bridge, placement of the bridge on an instrument is typically best left to professionals.
The engineering of cable-tension bridges – of the type that span rivers and carry vehicular traffic over them – is similar in that the tension has to be very closely engineered for it to work. What’s different with the violin bridge is that, as the supporting structure over which the strings are laid, it is not firmly anchored deep into the “ground” (instrument). The violin bridge is completely and easily removable.
This movability in the violin bridge is an essential characteristic. It would fail to provide that vibration transfer to the body of the instrument if it were glued or otherwise permanently affixed to the instrument.
But as any bridge engineer could explain, the supporting structure like the violin bridge needs to be perfectly (or as close as possible to perfect) perpendicular to the instrument body surface. Any kind of lean, any deviation from a 90-degree angle perspective, would likely be unsustainable. Importantly, when tuning any stringed instrument the shifting of the strings can affect this bridge angle; the violinist should therefore make manual adjustments to the bridge when tuning.
A collapsed highway bridge is a disaster, and particularly with early 20th century designs several did. A collapsed violin bridge may not involve the loss of life, but to a violinist it could lead to a disastrous situation nonetheless. Not only is the instrument at least temporarily unplayable (the strings would go limp), but could happen with such force as to damage the body and displace the soundpost in the interior of the violin body.
One mystery of music physics that remains to be solved – listen up, STEAM students – is whether there is value in drilling holes into a bridge. Discussion boards on various violin-interest sites offer a mixed review: some say it adds to the vibration transfer, others say it ruins a perfectly built violin bridge. One commenter even went so far as to say that drilling holes, then filling them with lead shot sealed inside, can produce “some really interesting buzzes and rattles.” Which isn’t called for in any of the compositions of Tchaikovsky, albeit one can always devise their own interpretations of the music.