Tune the birdcage action by removing the whole overdamper assembly,
birdcage and all.  Tune in the normal way but wear gloves so you can
damp the strings yourself as you tune.  If the strings are all rusty
or black don't bother with the gloves.  But mine are usually shiny new
strings and they will turn black or rust.

D. L. Bullock    Piano World    St. Louis