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Re: Starting year 3, now gouging and shaping....

Author: oboedrew
Date: 2009-08-21 19:17
Attachment: illustration one.jpg (19k)
Attachment: illustration two.jpg (18k)
Attachment: illustration three.jpg (19k)

cjwright wrote:

> Dan states a thinner gouge makes reeds last longer.
> I would argue that it is because as Mark points out,
> less cane needs to be scraped off, therefore leaving
> more external structure so that the reed doesn't
> collapse itself as quickly.

Ah, I see where you're coming from. But my own approach is a bit different. I'll try to explain.

"Collapse" can mean two different things to a reedmaker. I might say that a certain reed collapses easily. But if I don't clarify the meaning, that's a neutral statement. It can be a good thing or a bad thing.

A reed must readily collapse to produce sound. A quick overview, since we musicians don't often discuss the physics of sound production:

When you blow through an oboe reed, you increase the interior air speed. This decreases the interior air pressure (Bernoulli effect). The resulting differential in interior/exterior air pressure causes the blades to collapse inward toward each other. As the reed closes, the interior air speed is reduced, and the interior air pressure is increased, so the reed springs back open. The cycle continues, and this rapid undulation of the reed blades sets the air column within the oboe vibrating.

So...

On the one hand, collapse is good and necessary. The soft inner layer of cane is more flexible than the bark, so more bark on the reed means more air pressure is required to instigate this cycle of collapse and rebound.

On the other hand, the reed must spring open again. Permanent collapse is bad.

But permanent collapse (especially early in the life of a reed) is usually the result of excessive jaw pressure, or "biting." And biting is encouraged, even required, when unnecessarily heavy exterior structures (the spine and rails) hold the reed too open.

The spine and rails are desirable, but only to a point. They play a role in stabilizing a reed. But theirs is not (or should not be) the lead role. They are of secondary importance. I believe they are often left too heavy by reedmakers who lack other tools for stabilizing a reed. And when they are left too heavy, biting is encouraged, and reeds wear out quickly. A balanced reed, with thin rails, a light spine, and only a moderate opening, does not encourage or even allow biting. Such a reed can last a surprisingly long time with the right embouchure. It can (and should) be gripped just tightly enough to maintain an airtight seal. The smaller, weaker muscles of the lips should be used for all minor adjustments to intonation and timbre. The stronger muscles of the jaw can crush a reed. They're too clumsy for such subtle manipulations, and they're most often responsible for the sort of collapse that is permanent and undesirable.

So, how is stability achieved with only thin rails and a light spine? The secrets are in the tip and in the transition from tip to heart.

The tip should taper both vertically and horizontally. The very tip of the tip should be thinner than the back of the tip, and the sides of the tip should be thinner than the center of the tip. So the thinnest points of the tip (and of the entire reed) should be the front corners. And they should be remarkably thin: nearly transparent when soaked. The thickest point of the tip should be the center of the back of the tip, just in front of the heart.

The transition from tip to heart is also critical. This is the adjustment I believe is most often overlooked. And when it is overlooked, excessively heavy structures have to be left in the back to achieve stability. The right balance of definition vs gradation is critical. I find that reedmakers more often err on the side of too much gradation and too little definition. It is easier to blend the heart into the tip. It is more difficult to create a precise dropoff without cutting through the reed. Every piece of cane is different, every gouge is different, so adaptability is critical when creating this transition from tip to heart. I've attached three illustrations of a cross-section of a reed in profile. Usually it is best to avoid the extremes of illustrations one and two. The ideal is something more like illustration three: a precise dropoff approached at both ends by a gentle slope. None of these illustrations are to scale. They're just quick sketches.

Cheers,
Drew

www.oboedrew.com

Post Edited (2009-08-23 00:49)

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