Klarinet Archive - Posting 000438.txt from 2001/06

From: Eric Mumpower <nocturne@-----.com>
Subj: Re: [kl] open tubed vs. closed tube?
Date: Thu, 14 Jun 2001 14:44:08 -0400

> I just can't make this image fit with a clarinet, or see how there is any
> structural difference between the clarinet, flute, sax, oboe, etc.

Short answer: conical bores are Special. The clarinet does not have a
conical bore. All reed instruments are closed-tubes closed at the reed ends,
but conical-bore instruments behave very specially.

As was said in a previous email, the "stopped" end of the clarinet is the
reed-end. The clarinet is unique among the common western reed-instruments
in that it has a cylindrical bore. All the others have a conical bore --
oboe, bassoon, saxophone, sarrussophone....

Normally, stopped tubes can only play their odd harmonics -- first
(fundamental), third (an octave and a fifth higher), fifth, etc.

Due to some acoustic property of a cylindrical bore which I do not yet
understand, cylindrical reed instruments can play their even harmonics as
well. (The only intuitive explanation I've heard so far starts off by
pointing out that the wavefront inside the bore expands exactly as would a
circle on an expanding sphere. However, I've never had it explained to me
how, precisely, this makes any difference.) The math backing up this
principle is probably beyond most of us.

(As for flute, recorder, and pennywhistle (common reedless non-brass wind
instruments): they are all open at both ends.)

> So, what am I missing?

The clarinet is unique in that it's the only common instrument which has
surmounted the difficulty of bridging the gap between the top of the first
octave and the bottom of the third harmonic. This is a fundamental principle
of a cylindrical-bore reeded instrument, but most people don't notice it
because the clarinet is the only instrument which has evolved to compensate
for this gap.

And how does it do this, you may ask? Keys. Loads of keys. Think about how a
sax, oboe, or flute are fingered. There's no required additional keywork
between the top of the bottom register, and the next highest note (in the
second register, which uses the second harmonics). Even on a sax, all you
would need would be gigantic fingertips, and you'd be all set to play a
diatonic scale without using any keys.

But on a clarinet, everything between G and D (a fifth! Funny, that.) is
provided by keys which open holes beyond the reach of the tone-holes
directly covered by the fingers.

Thus, you have seen many examples of cylindrical-bored reed instruments,
because, in the largely keyless era prior to the 19th century, they were
still a viable model for making a flexible reeded instrument. Due to their
commonness, you take for granted the unique property which allows them to
work.

But there are very few non-folk cylindrical reed instruments other than the
clarinet, as none evolved capable of more than an octave until the advent of
reliable keywork. (This is my own theory, though for all I know it may
imitate others.)

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