Klarinet Archive - Posting 000970.txt from 2002/11

From: Bi6W@-----.net (Bill Wright)
Subj: Re: [kl] Brass vs Woodwind
Date: Tue, 26 Nov 2002 18:09:11 -0500

<><> Tim=A0Roberts wrote:
I have never encountered a description of a valved reed instrument, and
I have occasionally wondered why this should be.

Benade discusses this in "Horns, Strings, and Harmony" (the smaller and
more conversational of his two most popular books) --- starting on page
196 in the paperback edition and continuing through page 203, although
you'll also need to read a few pages about brass starting on page 164.

The grossly oversimplified explanation:

A full range of pitches on any wind instrument would require an
impractically long tube if we couldn't move between vibration modes
somehow (shift between registers).

Compared to woodwinds, it is physically easier to force a shift of
vibration mode in brass instruments by lip pressure alone. This is
because, despite the temptation to describe both woodwind and brass
instruments as simple open or closed cylinders or cones, brass bores
depart from the 'mathematical ideal' more than woodwind bores do. The
final result is that brass bores do not constrain the vibration mode as
rigidly as woodwind bores do.

This in turn allows a valved brass instrument to cover a full chromatic
scale with only seven semitones and appropriate changes in vibration
mode.

Since changes of vibration mode don't come as easily on woodwinds, and
therefore a combination of valves and lip pressure can't do the job on a
woodwind, why have valves on a woodwind at all?

(I'll probably take some flak for oversimplifying the issue this much.
Sorry.)

Cheers,
Bill

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