Klarinet Archive - Posting 000626.txt from 2003/08

From: Erik Tkal <bbtkal@-----.net>
Subj: Re: [kl] RE: Articulation problems
Date: Mon, 25 Aug 2003 14:40:54 -0400

At 11:13 AM 8/25/2003 -0700, you wrote:
>It is ***air pressure*** that closes the reed. It's true that the
>tongue does "something" to quiet the reed's vibration, such that our
>breath can do the rest. Whatever the correct name for this "something"
>may be, we seldom see posts that state explicitly that our breath
>provides the primary driving force. As obvious as this concept may be,
>it needs saying.

Yes, that is true. To be more specific, it's the Bernoulli effect that closes the reed, the same thing that lets airplanes fly. As you blow through the horn, the air moves along the inner face of the reed (facing the mouthpiece), but not the outer. Fast-moving air creates low pressure, pulling the reed inward. At some point, this reduces the airflow, allowing the reed to spring back, again increasing the airflow and the process repeats. The resulting frequency is a locking effect of this oscillation and the resonant frequency of the horn, defined by the shape of the horn and the current openings along its length.

The tongue can be used to modify this behaviour, specifically by stopping the reed from vibrating, most often keeping it from vibrating until you wish to start the note, and the sudden release of the tongue from the reed allows the reed to suddenly begin vibrating, giving an attack. It can also be used to stop a note, but I was taught that you should stop your breath to end a note, not use your tongue since that can sometimes give an extra unwanted attack sound. Of course in a fast staccato passage you are in effect using it for both.

The lips and your mouth also affect the sound because they contact the reed, both along the face and edges, changing the characteristics of the reed vibration and giving differences in tone.

Erik Tkal

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