Buzzing capo duplex

[James Ellis]

For those of you who are fighting the buzzing capo duplex:  It's a basic
design problem that's a carry-over from about 125 years ago.  

If you dress the capo bar to a smaller radius, it will stop the noise - for
a while - but then the strings will dig in, and the problem will come back,
worse than before.

If you increase the radius of the contact at the capo, it will lower the
friction, but you will have more surface in contact, and the buzzing will
come back.  

If you increase the contact angle at the capo, it will reduce the bleed
through, but it will also increase the drag in tuning, increase the strings
digging in, and increase string breakage.

If you mute the string lengths between capo and string rest, you will
deaden the tone, due to the fact that bleed through occurs both ways.

Several years ago, I developed a retrofit device that cured the problem
once and for all, but it has to be custom made for each piano, which is no
small task, and that's why I have not pushed it.  I'm still thinking of
ways that it might be simplified, but I'm not there with it yet.

You will find that the short string lengths that buzz are the ones that
happen to be resonant with some partial of the speaking length, which was
the whole idea of the duplex in the first place.

The late Ernie Juhn used to do a quick fix by putting a little "crazy glue"
on the string segments just in front of the capo bar - behind the string
rests.  He put just a little of it on the open lengths, NOT on the capo,
and NOT on the string rest.  What that did was change the mass of the
string just enough to get it off resonance with that particular partial,
and make it quit buzzing, without deading the tone very much.

The real solution is a complete design change, but that seems unlikely if
view of the touting of the duplex for so many years.  For years, I have
been tempted to write an article on the fallacy of the duplex scale, but I
know that would generate lots of flack, so I'm reluctant to do it.

Jim Ellis