Re: [Harp-L] Bending explained

[Vern <jevern@xxxxxxx>]

There is probably more to it than this, but here is how I understand bending: 

There are three resonant elements...the two reeds and the player's embouchure.
They are all linked together by the sonic pressure variations in the chamber.
Therefore, they do not resonate independently at different pitches.

To bend, the player changes his embouchure to a pitch lower than the draw reed's.
The embouchure is a Helmholtz resonator* whose frequency is lowered by increasing its volume and reducing the area of its neck.
In the harp, this is accomplished by dropping the jaw, lowering the tongue, and pinching the air passage at or near the mouthpiece with the lips.

The draw-reed-and-embouchure system resonates at a pitch lower than the draw reed's.
This can be done without the presence of the blow reed as in a chromatic or valved diatonic.

This pitch is closer to the pitch of the blow reed which starts vibrating.
The blow (opening) reed cannot start vibrating from airflow alone, but it can be excited by sonic pressure variations in the chamber.
Once it gets going and starts swinging through the slot, it can receive energy from the airflow as any reed does.

Now the two-reed-and-embouchure linked system resonates at an intermediate pitch.
The embouchure can influence this pitch, but it must be...
..... higher than the blow reed's and lower than the draw reed's.

* See "On the Sensations of Tone" by Hermann Helmholtz, Chapter III and Appendix II (Published in 1877 !)

Vern

On Mar 19, 2010, at 8:13 PM, John Frazer wrote:

> FM, Michael. It is F. M.
> 
> 
> On 3/19/10 10:26 AM, "harp-l-request@xxxxxxxxxx" <harp-l-request@xxxxxxxxxx>
> wrote:
> 
>> How does the blow reed take over?  How does bending fool the blow reed
>> into vibrating quicker and producing a higher pitch?  What does the
>> sympathetic vibration of the draw reed have to do with it?
> 
>