bow strokeWe’ve all seen string players (maybe you’re one yourself) producing beautiful sounds with that fantastic combination of instrument and bow. Have you ever wondered how the bow, a seemingly un-musical length of wood and hair, can coax an instrument into producing such sounds? The answer is both simple and complex.

Bow Stroke Energy

A stringed instrument makes sound when one or more of the strings are vibrating. To start vibrating, the string needs energy. This is the whole purpose of a bow: it adds energy into the system of the instrument to make sound. Short bursts of energy are nice, but they make a sound that quickly dies away (pizzicato notes on a violin, for example, or a plucked guitar). The advantage of a bow is that it provides a continuous source of energy resulting in a sustained sound. The bow’s length of hair continuously excites the strings as it’s pulled across them.

When the bow is pulled across the string, sticky rosin helps the horsehair grab the string. The friction between the hair and the string pulls the string a little to one side. When the string reaches the limit of how far it can stretch, it snaps back. The bow grabs the string again, and back and forth it goes. The string is now vibrating (and therefore producing sound) because of this motion. This cycle of sticking and releasing can happen about 20 times each second.

The physical principal that allows this action to happen is called the stick-slip mechanism. Though you may have never heard of it, you have certainly heard what it does. Every time a shoe squeaks or chalk screeches on a chalkboard, that’s the slip-stick mechanism in action.

Putting It All Together

bow strokeWe all want an instrument that sounds better than a screeching chalkboard. Thankfully, an instrument can create beautiful sounds because of the interacting parts of a very complex system. These components include the wood of the instrument, the air inside it, the bridge, the strings, and–last but not least–the bow hair and stick. Though it may seem that the shaft of material pulling horsehair across the strings wouldn’t matter much, it actually does. Turns out the resonant properties of the material used for the stick feed into that complex system, and have a profound effect on the quality of the sound. We’ll explore the parts and qualities of the bow further in another post.

Violins, violas, cellos, and basses are all played with bows that differ in length and weight. Because a larger string requires more energy to start the string vibrating, we see a general rule in play: the larger the instrument, the heavier the bow. This extra weight usually comes by way of a larger bow stick.

What About Bow Size?

But what about bow length? Smaller instruments and strings require more speed in the bow stroke to produce the same amount of sound. If all bows were short, viola and violin players would have to change bow direction more frequently (making them cranky). The solution: longer bows.

If you are in need of a good quality bow, we highly recommend our Pierre Martin pernambuco bow. These significantly help sound quality production at an affordable price.

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14 replies
  1. Stradplayer96
    Stradplayer96 says:

    I find that a lot of it has to do with the flexibility and stiffness of the fingers. The fingers are like shock absorbers and depending on how legato or staccato or spiccato you want your stroke to be, you adjust your fingers. It’s a conscious effort to switch between loose fingered legato to arm motioned spiccato all while flattening the bow hair to the string to create more surface area for the spiccato.

  2. thinkoutsidethebachs
    thinkoutsidethebachs says:

    I used to think of bowing as just a way to produce sound, not a way to manipulate tone. I’ll be working to better my tone production through the bow arm.

  3. DeaconBlue
    DeaconBlue says:

    Why do all bows use horse hair? I would think that a synthetic material could be developed that has the required properties, but be more consistent that a natural product like horse hair.

    • Hexensohn
      Hexensohn says:

      There exists a few synthetic hair bows on the market. Strings players tend to be sticklers for tradition so that might be a factor in why they aren’t more widely used. That’s why you still see gut strings on the instruments of period players. It also might be a case of ain’t broke so don’t fix it.

  4. Will
    Will says:

    I’ve started using a pernambuco bow. I like it’s flexibility and, when needed for spicatto, it is “springier”. I now use my old brazilwood and/or fiberglass bows for wall decorations or photo props.

  5. Kevin DeSilva
    Kevin DeSilva says:

    Thank you for this – had a few ideas previously but learned a lot … and it is good to have this understanding.

    In counseling, some of us work with what we call the Rational Mind and the Trans-Rational Mind;
    The Rational Mind is able to embrace the factual and mechanical – mathematics, historical facts, bridge building and the like … the physical; the mortal … stuff with dimensions.
    The Trans-Rational Mind is able to embrace the aesthetic, the mythic, the emotional … the spiritual; the eternal … stuff that can not be put into a box and, therefore, can not be captured by any language (explained).

    As humans (this also works for all other forms of life), we function best when we are “balanced” …. therefore, to embrace BOTH our Rational and our Trans-Rational Mind at the same time is best.

    So much of the enjoyment, I find, that is part of this journey with the Violin is working with the Trans-Rational side …

    With this explanation, you explain the physics of creating sound (with a stringed instrument) … Mechanical Stuff! – The Rational Mind loves this!

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