Larry Lobel was asking about repairing a loud buzz in the soundboard.
The kind of buzzes caused by loose ribs are always the ones that seem
tight. If they didn't, they wouldn't buzz, of course. Ribs that you can
get a shim between aren't close enough to the soundboard to buzz at all.
There are many ways of fixing it, so it depends on your tools, materials,
and etc. But once you locate the central point of the noise, mark it and
tip the piano on it's side so you can get to the problem easily. Once
tipped, play the strings with an external hammer you can hold in your
hand to see that it still buzzes. (The keys won't play on their sides).
By drilling a very tiny (almost invisible) hole through the rib and
soundboard, you are able to insert a piano wire. By this method you will
be able to draw the rib together with the soundboard by tying something
to the wire and backing it with a fiber washer with a small hole. On the
other side (rib side) of the hole the wire runs into a block having a
tuning pin. Wrap the wire around the pin and tighten it down.
Now strike the strings again and see if you can get it to buzz. When you
find the central spot for sure, then you can fix it by forcibly
separating the rib from the board and re-gluing it. Do not use "tightbond"
or Elmer's glue! These kinds of glue are not hard, and they "creep" over
time, gradually re-separating, if there was tension there that would tend
to shear their joint. However, hard epoxy is just fine to use. Or if
you are very experienced with the different kinds of cyanoacrylates and
hardeners, they are fine glues to use for this, too. They will "wick"
into thin joints too small to see, and repair them instantly.
The main thing to do is to use the products you are comfortable with,
other than those that are stretchable, which will eventually break again.