Re: [Harp-L] How does bending actually work? (the physics)

[Arthur Jennings <timeistight@xxxxxxxxx>]

I am not a physicist, but here's what I think is happening:

There are three resonances interacting in an unvalved bend: the draw reed,
the blow reed and your mouth. As you lower the resonant frequency of your
mouth cavity, you force the draw reed to vibrate at a lower rate. (This is
what is happening on a single-reed bend on a valved harp.) As the pitch gets
lower, it gets closer to the resonant frequency of the blow reed, which
excites the reed and causes it to vibrate.

You can observe this sympathetic vibration effect on a string instrument. If
you play an 'A' or the low 'E' string of a guitar and watch closely, you can
see the open 'A' string vibrate along with it. In fact, if you stop the note
on the sixth string you'll continue to hear it from the still vibrating
fifth.

On Fri, Mar 19, 2010 at 10:02 AM, michael rubin <
michaelrubinharmonica@xxxxxxxxx> wrote:

> I have often explained to my students that when draw bending, what we
> think of as the blow reed takes over the vibration and does the bend
> sound.  I take the cover plates off of a harp, I bend, I put my finger
> on the draw reed, stopping the reed's vibration and the bend continues
> to sound with vibration on the blow reed's part while the draw reed
> has stopped.  This has satisifed many students, but today I have met
> my match.
>
> 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
> symathetic vibration of the draw reed have to do with it?
> Thanks,
> Michael Rubin
> Michaelrubinharmonica.com
>



-- 
Arthur Jennings
http://www.timeistight.com