Duplicity on a Grand Scale

[Ron Nossaman]

Hi gang, 

It's me again, and I've got something for you. Out tuning today, I got to
dinking with the duplexes, and I observed an interesting thing or two. You
can too, if you bother to try. 

The first thing I did was chose a noisy string and touched the front duplex
while playing the note. The tone got considerably clearer. I then plucked
the speaking length while holding the key down to keep the damper up, and
not touching the front duplex and the noise was back. No surprises here.
Then, still holding the key down, I plucked the duplex and the speaking
length sounded at the fundamental. Cool! Proof positive that string energy
bleeds past the v-bar to the next segment. This was a low bearing angle,
long front duplex, so that wasn't any surprise either. I located the longest
duplex and plucked that. The speaking length fundamental sounded, but there
was a lot of added garbage coming from the front duplex segment that
rendered the combination of the two less than pleasant. What do you suppose
happens at the agraffes? I then went down to the tenor section and plucked
the, roughly, 10 mm long segment between the understring felt and the
agraffe. The speaking length sounded the fundamental. Really cool. The
bearing angle here was much steeper than in the treble ( about 20 degrees),
and the segment was super short and muted by cloth, and the brass of the
agraffe was much softer than the v-bar, but it still worked. What the heck,
I thought, let's try the bass. Yep, same thing, in spite of the even steeper
bearing angle through the agraffe. 

Later, I tuned a new console. No intentional front duplex to dink with, but
there was that nice short, high bearing angle segment between the v-bar and
the pressure bar. Key down, I reached in with my junk pocket knife blade (as
opposed to my surgery blade, but that's on the other knife anyway), and
plucked the segment. The speaking length sounded at the fundamental. Well,
in the interest of symmetry, I've got to try the bass too. Key down, I
plucked the segment between the upper bearing pin and the tuning pin and the
speaking length didn't sound like anything I could identify because the
segment I plucked drowned it out and turned the combined sounds into
garbage. Playing the note normally, I couldn't specifically pick out the
sound of the "duplex" (what's that little sucker called anyway?), but I
begin to wonder how much, if any, of the bass garbage we can't seem to tune
out comes from this.  

Anyway, the on the spot conclusions were that increased bearing angle
doesn't entirely stop the energy leakage past the agraffe or v-bar. With the
sampling I had, I can't separate the effects of angle and duplex length, but
it is quite obvious that the shorter duplexes are quieter at a low bearing
angle, and it's reasonable to expect that a higher angle will result in
better termination. 

Entertainment is where you find it when tuning.

 Ron