Article about bridge agraffes - function, types

[Calin Tantareanu]

> -----Original Message-----
> From: pianotech-bounces at ptg.org 
> [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman
> Sent: luni, 20 noiembrie 2006 19:43
> To: Pianotech List
> Subject: Re: Article about bridge agraffes - function, types

> 
> Hi Calin,
> I see it somewhat differently. The wood acts as a damper, yes, 
> but not for high frequencies, but rather for bleed through. 

Interesting point.

> The short segments within a bridge agraffe are too short to 
> sound audibly. They are, however, long enough to transmit 
> string motion, via rocking on the bearing points, through to 
> the back scale. 

Quite possible.

> This doesn't happen in a conventionally pinned 

It doesn't, but this doesn't mean that the energy that would bleed through
the agraffe to the backscale is conserved in a traditional pin/cap device.
It is just lost there because the string segment between two bridge pins is,
in effect, a damped string segment.
So the bridge agraffe appears, again, as a device that can put some of the
energy lost with a traditional termination to an audible use. If the result
is pleasant or not, worthwile etc, remains to be seen.
But the Steingraeber piano was wonderful, so agraffes seem to have a lot of
potential in the hands of the informed piano designer.

> bridge, so with bridge agraffes, you get a direct relationship 
> between the string played, and the back scale of that note. 
> This is the way front duplexes work, only it's on a moving 
> bridge in this case instead of a more solid plate, and the 
> deflection angles are typically shallower in the bridge 
> agraffe, increasing the effect. It isn't a problem in the 
> lower portions of the scale because the back scale is 
> typically braided off down there already to prevent noise 
> being generated by the long back scales. I would bet that 
> braiding off the back scale would immediately kill that 
> objectionable "agraffe" noise. But then you wouldn't get the 
> sound from the open back scale of a conventionally pinned 
> bridge, hence the rubber or felt dampers in the agraffes. They 
> kill the bleed through noises without killing the typical and 
> "normal" open back scale noise.

I'm not sure what you mean by "agraffe noise". Is it unwanted partials or
something else?

Calin Tantareanu
http://calin.haos.ro
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