Klarinet Archive - Posting 000587.txt from 1998/07

From: Jonathan Cohler <cohler@-----.net>
Subj: [kl] The LH Sliver Key and the Physics of Closed Tone Holes
Date: Mon, 20 Jul 1998 11:44:25 -0400

The LH Sliver Key
-----------------

Keys have been progressively added to the clarinet over time to make
substantial improvements in the ease of playing. One could argue that many
of the keys on the instrument are not "necessary", because people played on
instruments with many fewer keys back in the days of Mozart and Beethoven.
Of course, then again, all one has to do is go listen to someone attempting
to play on those old instruments to realize why the keys have been added.

There is an important reason for the LH sliver key (which has already been
mentioned, I believe). It allows one to finger chromatic passages entirely
in the left hand. This is important because one of the major technical
problems that all human beings encounter is the synchronization of the
right and left hands.

The right hand is controlled by the left side of the brain, and the left
hand is controlled by the right side of the brain. When the two hands must
move in a synchronized fashion, a signal must cross between the two sides
of the brain. There may be some brain specialists or doctors on the list
who could elaborate further, but my understanding is that the amount of
time for this signal to be transmitted is substantial (on the order of 10s
of miliseconds).

It is precisely because of this signal delay time that any synchronization
of left and right hands is so difficult. You can demonstrate this to
yourself by trying the following excercise.

1. Trill from fourth-line D to fifth-line F. This involves
the synchronized motion of the second and third fingers
of the right hand. This is quite easy to do.

2. Trill from fifth-line F to A one line above the staff. This
involves the synchronized motion of the first finger of
the right hand and the third finger of the left hand.
This is very difficult to do and sustain.

The LH sliver key provides an additional mechanism for eliminating two-hand
finger synchronization in numerous instances. It also provides some
critical trill fingerings. I think it would be fair to say that in
virtually every piece I play that has Eb first line or Bb above the staff,
there are important uses of this fingering.

Of course, it is possible to work around this fingering using the side
fingering, but it is clearly much more difficult to do so, and dramatically
increases the probability of error to do so.

The Physics of Closed Tone Holes
--------------------------------

A tone hole covered at the top definitely has a noticeable effect on the
instrument. (See "Fundamentals of Musical Acoustics" [Benade, Dover] pp.
448-449 for more details)

Imagine a cylindrical tube with tone holes in one section of the tube.
When these holes are covered on top, the tube behaves acoustically as if
the section with the holes was slightly longer and slightly larger bore.
The increase in length obviously lowers the overall pitch, and the local
change in bore size modifies the relative positioning of tube resonance
peaks which can dramatically change the playing characteristics of the
instrument.

The magnitude of the effect is controlled by four parameters:

1. the bore diameter 2a
2. the tone hole spacing 2s
3. the tone hole diameter 2b
4. the pipe wall thickness t

Both the length of the tube segment and the cross-sectional area of the
segment are enlarged by a factor E given by:

E = 1 + ((1/2)*(b/a)^2*(t/2s))

According to Benade, "For most woodwinds, the change implied by this
formula ranges from 2 to 5 percent."

Therefore, if you plug up the LH sliver key hole, you will make a
noticeable change in the pitch and playing characteristics of the
instrument. It may be the case that these changes are small enough to deal
with from the players point of view, but there is no question that a
high-quality instrument was designed with the hole as part of the overall
design. In other words, plugging the hole has noticeable effects on more
than just that one note.

Designing an instrument with one hole shared by the side and sliver keys
does seem to be a good idea on the surface. This would give the player the
same sound and intonation for both fingerings, of course.

I am no expert on the mechanical issues involved, however, it must be a
daunting task or we would probably see more of these mechanisms on the
market today.

---------------------
Jonathan Cohler
cohler@-----.net

--------------------
Jonathan Cohler
cohler@-----.net

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