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Klarinet Archive - Posting 000302.txt from 2010/11

From: Tony Pay <tony.p@-----.org>
Subj: Re: [kl] What is a clarinet?
Date: Fri, 19 Nov 2010 12:29:40 -0500

On 19 Nov 2010, at 16:24, George Kidder wrote:

> At 06:30 AM 11/18/2010, Joe Wakeling wrote:
>
>> On 11/18/2010 01:43 AM, Dan Leeson wrote:
>>
>>> If you will take a clarinet, remove the mouthpiece, fashion a cork with a
>>> hole in the center, place the cork in the upper end of the barrel, and
>>> insert an oboe reed in the hole, playing it will result in the instrument
>>> overblowing an octave. What this says is that the characteristic of
>>> overblowing a 12th must come not from the straight tube but rather from the
>>> mouthpiece and single reed combination, though I have no idea what causes
>>> the mouthpiece and reed to behave the way it does.
>>
>> That'd be because the effect of having a consistently narrow length of
>> tube (the oboe reed) connected to a much wider tube (the clarinet bore)
>> is effectively turning the overall bore shape into something that is
>> approximately a cone rather than a cylinder ...
>
> The same thing occurs with a contrabassoon reed, which is closer to the
> "right" size.

Well, in 2003, you wrote

> So, vide your previous post, get yourself a bassoonist friend and a cork!

...and I then wrote, slightly edited:

> Yeah, I did, as previously promised. So, we tried a bassoon reed
> (though not yet a contrabassoon reed, though we have a contrabassoon in
> the ensemble next week.)
>
> This bassoon reed was inserted into the top of a C clarinet barrel, with
> the socket filled with blutak around the reed. (So, a jump
> discontinuity of boresize at the top of the barrel bore, where the
> mouthpiece usually takes over.) Period instrument, so few holes and
> relatively simple tube.
>
> In this first experiment, we didn't attempt to measure the pitch of the
> lower register, though we'll perhaps try again tomorrow. (In fact, in
> the next experiment, in order to make some comparison with the standard
> pitch as played with clarinet reed plus mouthpiece, my idea would be to
> join the bassoon reed to the slot of the mouthpiece in such a way as to
> make the volumes of the two systems roughly equal.)
>
> We found that the overblown pitch is highly labile, in the sense that
> you can achieve an octave, and with a different embouchure also less
> than an octave; BUT you can also bend the top note at least a fourth
> higher without changing the mode of oscillation.
>
> What that indicates to me is that the reed and tube aren't strongly
> coupled, so the description 'overblows an octave' is not really accurate.
> Something that 'overblows' over such a wide range isn't really
> 'overblowing' at all.
>
> Then we tried an oboe reed. This proved incapable of sounding any sort
> of fundamental. The effect was of a reed 'crow' inside the clarinet
> tube. In effect, the reed wasn't 'seeing' the clarinet tube, and its
> behaviour was dominated by its own vibrational characteristics.
>
> A narrower clarinet bore might give a different effect, but I imagine
> that it would be equivalent to using a larger reed -- which we
> already tried by using the bassoon reed.
>
> In a way, I suppose none of this is surprising. Real instruments are
> designed in such a way that the reed and tube vibrations are strongly
> coupled, and it's that coupling that allows the simple mathematical
> analysis to work.

Tony
--

Tony Pay
79 Southmoor Rd
Oxford OX2 6RE
tel/fax +44 1865 553339
mobile +44 7790 532980
tony.p@-----.org

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