Matt,
I know the chien buzzes at the trompette string pitch
I have seen oscilloscope traces of this (uni research project)
Its a nasty square wave with lots of contact bounce
The fundamental is however the string pitch
The usual pitch drop may to be due to the increase in sounding length while
buzzing
When not buzzing the length is defined from the ear to the chien
When buzzing the length is increased by the distance between the chien notch
and its fulcrum on the mouche bridge
The chien notch is no longer the node point
I did some measurements on the pitch drop - chien length
The numbers worked out pretty well
Short chiens produce less pitch drop
A complicating factor is that light, crisp trompettes produce much less
pitch drop
I guess this is due to the chien foot staying more in contact with the belly
and the node moves less
Graham Whyte
----- Original Message -----
From: "Matthew Szostak" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, July 26, 2006 6:47 PM
Subject: [HG] String setup / adjustment question?
At first I was considering this a discussion for makers, but it seems to
me now that it's more than that. This could, and dare I say, should, be
of interest to anyone who plays hurdy-gurdy and wants to keep their
instrument sounding and playing its best.
As most of us understand, there are certain undesirable sounds associated
with the hurdy-gurdy that can generally be blamed on problems with string
pressure. There is a certain ideal pressure of string against wheel that
provides the right sound quality. I know that there is some room for
adjustment based on personal preference, but I think that most of us are
aware that, for example, if the melody strings press too hard against the
wheel, they will get scratchy-sounding and the upper notes on the keyboard
will likely not sound at all - we shim and move on. Also, if your low
wound drone strings press too hard against the wheel, then the pitch of
the note will vary widely with changes in wheel rotating speed. Simple
shimming might not be the easy answer here, but again, usually the culprit
is too much pressure, as long as everything else is in proper adjustment.
I currently have a hurdy-gurdy that is in need of some basic adjustment to
get it up and running, but I'm having tuning problems which won't let me
alone. First of all, I adjusted the pressure of the melody strings on the
wheel to where they should (in my opinion) be, then I adjusted the cotton
on the strings and the rosin on the wheel so that I get a nice clean sound
over the whole range of the keyboard - no problem.
Here's where things become interesting. First of all, the low drones now
tend to change pitch quite drastically when I make minor changes in
cranking speed. If I reduce the pressure, by even a little bit, the
sound of the string looses its fullness, it breaks into harmonics, and it
won't start playing cleanly from a full stop without giving it a pluck to
help it along. I cannot find a middle ground.
But wait, there's more! This next particular problem was discussed here
before, but I'm not sure a satisfactory conclusion was ever reached. When
the chien is made to buzz, the pitch of the sound drops quite
dramatically. Now I know there has been disagreement, or at least
inconclusive discussion, about whether the frequency of the tapping chien
is the same as the vibrating frequency of the string; either way, the
overall effect here is that the trompette drone is tuned to one pitch, and
when the wheel rotating speed is increased a bit and the buzz produced,
the pitch of the combined sounds of string and chien is clearly reduced.
I've heard this effect on a number of recordings (even *gasp* Patrick
Bouffard), although it's rarely pronounced enough to distract or bother
me. But this instrument is suffering for it.
At the time Marcello and Theo exchanged some interesting ideas, but my
question is: why would such problems appear now, years after it was made?
The geometry of the chien / string anchor point hasn't changed (there's no
obvious visual difference, anyway), but this hurdy-gurdy didn't have this
problem before. Is there any conclusive advice that can be given to solve
this problem, especially with the trompette? This thing sounds great when
you get it all tuned up, but as soon as you start buzzing, the drones go
sharp and the trompette goes flat and it's a real mess! Before I start
moving string anchor points around, I thought I'd see if anyone might have
some fresh ideas about this...
~ Matt
