Article about bridge agraffes - function, types

[Ron Nossaman]

> The pin is harder, but the wood which touches the string acts like a damper
> for very high frequencies. I exaggerate this to make my point, but that's
> what happens.
> Piano makers have long used the hardest woods in the top treble caps. I
> believe they recognized the need for a very stiff material there, to
> minimize energy loss. The bridge agraffe is another quite efficient) way of
> reducing energy losses where it matters most.


Hi Calin,
I see it somewhat differently. The wood acts as a damper, yes, 
but not for high frequencies, but rather for bleed through. 
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. This doesn't happen in a conventionally pinned 
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.

My take,
Ron N