Chapter 1.1

The Response

For the sake of clarity, let us first consider a single note. It begins with silence. The bow rests on the string. Since there is rosin on the bow hair, it adheres to the string. Now the player moves the bow. We can observe this as though it were happening in slow motion.

The bow accelerates, like a car starting from a full stop. But the hair still adheres to the string. The bow pulls the string in the direction of its movement. The further the string is drawn, the greater its tendency to disengage from the bow hair. The hair also pulls on the bow, which also yields, like the bow used to shoot arrows. But the string's tendency to disengage soon overcomes the bow's adherence to the string. At this point the string snaps back. But the bow continues moving, driving the string along like a top. There it is! The vibration begins. The way the bow causes the movement of the string to accelerate is what we call its response.

At this point a few words need to be said about the bow hair, since it is the hair, not the stick, that makes contact with the string. It matters a lot how thick the individual hairs are, how many there are, and whether these are evenly distributed. A bad job of rehairing can affect performance negatively. Reportedly, Mme. Tourte herself washed and selected bow hair with the greatest care.

Every bow has its own response, which is only achieved when the bow is properly rehaired. Just as a car needs the right tires, a bow needs more or less, thicker or finer hair. The stronger the bow, the denser the hair that is required, and the more of it that is needed.

Hairlint rests on the stringHairlint rests on the string

Let us now consider how the hair rests on the string. The string's surface forms a curve. The surface of the hairlint is flat. If the hair is tight, the point of contact between the string and the bow hair is very small. If the hair is looser, and more yielding, it can envelope the string a bit, increasing the contact surface. Therefore, a softer bow can set the string in motion more easily. In any case, more effort is needed to move the string with a firmer bow.

The response is almost or entirely inaudible, but its effect on the sound is not. The vibration that ensues depends on how aggressively the string is activated. But there is no ideal response. The best that can be hoped for is a good compromise. Above all, the bow must be compatible with the instrument, because the instrument has its own response, which affects the vibration just as much. In addition, a high note has a shorter response than a lower note, because the wave length of the higher note is shorter (Firm bows therefore work usually better for high notes, soft bows for bass notes). It also matters where the bow makes contact with the string. The string has more room to vibrate over the fingerboard than near the bridge. That affects the relationship between the grip of the bow on the string and the capacity of the string to return to its original position.

The screw makes it possible to tighten or loosen the bow, but what ultimately matters is how the bow is made, and how and where it yields. Usually, it yields the most at its weakest point, which is right behind the head. Every time a new vibration is produced, the tip of the bow bends a bit. What matters here is not so much the strength of the wood as the relationship of the weakest point to the rest of the stick. There are bows with a short, particularly weak point behind the head, and others where the stick broadens more evenly, leading to a different kind of response.

It is hard to express this in words, but what can be said is that a short, hard response generally allows for more transparency, but increases the danger of incidental noise. A softer, slower response results in a rounder sound, but makes it harder to tell exactly when the tone starts. In the end, players have to pick a bow compatible with them and their instrument.

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