[pianotech] The buzz that comes and goes...

[Ron Nossaman]

pianofritz50 at aol.com wrote:
> I have a customer who's 1+ year old Baby Grand has a buzz.. particularly 
> at 3-4 keys around G5.  But when I was sent out on a warranty call the 
> buzz was gone.  I went thru a Pitch Raise and Tuning (since it needed 
> it), and "nothing".  It sounded lovely.

I've found the usual lock, soundboard foreign object, window 
pane, picture, metal box on top, etc., and even a heating duct 
in the wall behind the piano. The worst killer buzz ever was 
in a Yamaha grand. We chased the thing for months without ever 
getting it to make the noise when I was there. It came and 
went at what seemed like random intervals. It FINALLY turned 
out to be the lid locater pin. With the lid down, it was 
centered in the bracket hole closely enough that it alternated 
between no contact, to enough contact to buzz, to contacting 
firmly enough to not buzz. A couple of degrees of temperature 
change, or a very slight humidity change, or both, moved it 
enough to make it come and go. A couple of thousandths of an 
inch would do it. I finally got lucky enough to get there 
while it was still buzzing, had her hit keys while I stalked 
around listening, and found it when I touched the lid. I put a 
little sliver of cardboard in two of the three screw holes of 
the pin mount, rotating the thing off center of the bracket 
enough that the pin makes contact with the bracket all the 
time, and the buzz never came back.

Since it happens through a range, it's a sympathetic, not a 
damper wire, bridge pin, duplex, etc., specific to a single 
unison. That means it could be ANYWHERE. I wish you luck. It's 
demoralizing when you can't get even a confirmed sighting - 
like hunting Bigfoot.
Ron N