Strange Buzzing in Klunker Trichord

[Greg Livingston]

Today I met a 1900's woofer- a sadly neglected old upright, filthy, dusty, 
but needed for piano lessons in a few weeks.  All seemed to go well until I 
hit the lowest trichord and got a terrible buzz.
After some detective work,

-it's the middle string only; the left and right are fine, and the next 
trichord is fine, too.
-bridge seems okay; pushing on it around the hitch pins with a screwdriver 
made no improvement
-no cracks in the soundboard
-enough clearance with the plate strut
-sanding and needling the hammer and damper made no change
-with the lamp below and the flashlight down from the top, I could see no 
obstruction or foreign object.

Any ideas?  I'd hate to change the string since I had already pulled the 
action and because the action bolts are bent, I could hardly get the action 
back in.  (I've never changed a string in the middle without pulling the 
action.)

Gratefully,
Greg Livingston

_______________________________________
Gregory P. Livingston, Piano Tuning and Service
781-237-9178
Piano Technicians Guild, associate member
(Boston chapter)

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Always remember September 11, 2001