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THE CLARINET BARREL
from "Clarinet Acoustics" by O. Lee Gibson, published by Indiana University Press
In their effects on the modal frequency ratios of the clarinet, the mouthpiece and the barrel need to be treated as one variable unit.
With respect to intonation, given a prescribed length, modal ratios supplied by a barrel are determined by the total volume enclosed within it (and the mouthpiece). The larger this area the greater the frequency separation between the upper first and second modes. Also, as detailed in Chapter 9, the farther up a tube an enlargement occurs, the more specifically it affects higher-mode frequencies such as those of the third, fourth, and fifth modes. A pronounced reverse-conical (Moennig) bore in the barrel can therefore raise the upper third-mode pitches slightly while holding down those of the upper second mode.
Tone is complexly affected by the weight of the barrel; the presence or absence of a dually tapered venturi in the barrel; a slight cavity resonance, which may be promoted by a reversed cone in the barrel as well as by another in the LH joint; and the finish of the inner surfaces of the barrel. Less weight produces more brilliant and less massive tones (as is the case with the entire body). The presence or absence of metal rings contributes to this totality.
Flexibility and brilliance will be promoted by the presence of a dually tapered venturi in the barrel, as compared with a linear taper. With the dual taper the upper portion of the bore decreases from a slightly enlarged top to a chosen midpoint, followed by a less rapidly decreasing lower portion.
Wind resistance and wall losses are affected by weight, enclosed volume, and the quality of the inner surfaces.
It is wise to reduce the bore of the barrel slightly when it is lengthened, since the added length provides an increase in a normally enlarged portion of the bore. (Consider a decrease of 0.03 mm. per added millimeter of length.)

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