Buzz problem

[Maxpiano@AOL.COM]

I ran into a problem today that I could not correct despite an hour of trying 
before tuning the piano.  I was stymied despite my nearly 50 years' 
experience tuning pianos.  Has anyone on the list experienced the same and 
found the answer?

The piano:  a Baldwin Howard spinet, S/N 1,095,157 (1976).  A rattling buzz 
with hollow, false tone in the first octave or so of the bass indicated a 
loose bass bridge.  Not so.  Bridge was tight to the shelf, the shelf tight 
to the sound board.  Yet pressure against the bridge would restore the tone 
just as with a loose bridge.  Seating strings made no change.

Pulled the piano out from the wall.  No junk lying there, no loose ribs, no 
separation of the sound board from the liner.  I scraped the sound 
board-to-liner joint for loose glue.  I got a bit but there was no change in 
the tone.  I checked the sound board button screws, all except one were 
tight.  Anchored that one and still no change.

I noted one curious fact:  from the front, I could stop the buzz by pressing 
elsewhere, such as on the tenor bridge above the "loose" area and on the 
board in the same area.  Checked the area between plate and board with a 
flexible steel, but found nothing.  Checked with a mirror to see if the plate 
was coming loose bottom, but its "nubs" were right up against the board.

>From the back, with the customer banging low C, I was able again to silence 
the buzz by pressing in the general area of the bass bridge.  Then I became 
aware that there was a scraping, grating sound as I pressed in on the board, 
and again as I released it.  (I recall a similar experience with a new 
Baldwin grand in the early '70's; I never did hear how the dealer handled 
it.)  There is a hole in the sound board (plate bolt) in this area, but there 
is plenty of clearance with the bolt.  

The board gives the impression of solid spruce, but the joints visible in the 
front do not correspond with the joints visible from the rear. Am I dealing 
with a laminated board and could it be delaminating?  If so, what can be done 
about it?  The cutouts around plate bolts show no separation, yet the area 
around the plate bolt between bass and tenor bridges is the area where 
pressure silences the buzz.

Since I am on a trip, the customer is over 100 miles from my home and I will 
be passing by their home on my way back in two days (Friday), I would 
appreciate any input from the group.

Bill Maxim, RPT
Columbia, SC