Greetings,  In cases where a piano part is intended to be permanently
attached and there is no concern for future disassembly, I feel that it
is appropriate to use the best and strongest adhesive available.  Brass
is not the original part to begin with, so originality is not of
concern here but rather a permanent solution.

Brass is not that easy to glue to.  It seems to hold contaminants well
and will appear to be glued but fail in the future if not properly
prepared.  Roughening the surface and cleaning with 99% isopropyl
alcohol or other cleaner that leaves no residue are essential.

Then I would use either a good quality epoxy or a rather remarkable
adhesive called "Depend" that is made by Loctite.  It is expensive.
It is pretty amazing how well it sticks to brass and other difficult
to bond surfaces.  It is supposed to stick to (and testing shows this
to be true) wet and greasy surfaces.

I have used "Depend" to stick plastic to glass in an application where
all other adhesives failed in time because of constant tension in the
joint and full sunlight exposure.  The "Depend" is still holding on.
It would probably be a good idea to seal the wood surface prior to
gluing so the joint does not become starved by the wood absorbing the
glue.  Probably a coating of the same glue itself would be best.

Another possibility would be to use screws to hold the plate in place,
with just a sealer such as shellac but not depending on it for bond
strength.

Best regards,
Spencer Chase
Laytonville, Calif.
http://www.spencerserolls.com/

 [ "Depend", Loctite Product 330, a one-component urethane
 [ methacrylate ester, is a general purpose structural adhesive.
 [ Ref. http://www.loctite.com/int_henkel/loctite_us/index.cfm
 [ and http://tds.loctite.com/tds5/search.asp  "Depend" is a
 [ trademark of Henkel Loctite Corp.  -- Robbie