Two more cents worth on the difficulty of drilling a hole in a damaged
screw for application of an easy-out.  The solution:  Just as you would
with drilling any metal object, first use a center punch, if feasible.

I realize this will not work with a floating screw that would be
knocked through a piece of wood and disappear inside the piano.

Punched or not, use the smallest drill bit necessary to clear the sides
of the slot, so that it will not tend to wander.  Starting with a
sharp, very small bit requires much less pressure upon the work, is
easier to control, and will result in a well centered and straight
starter hole.

Drill the hole to the depth you wish, followed by increasing sizes of
drill bits until you achieve the diameter of hole desired.  Decrease
the depth with each larger diameter bit to accommodate the taper of the
easy-out.

On machine screws that are stuck quite tight into a metal hole, make
the hole large enough to accept  the largest sized easy-out practical
for the application. Easy-outs can snap off under too much torque, so
use the largest size possible for the job at hand.

Let the screw cool off after drilling before using the easy-out, so
that it can contract a bit.  Also soak with rust-buster or some
equivalent.

Again - Use the largest easy-out possible in the screw.  If the screw
is REALLY jammed in the hole you can break an easy-out if you apply too
much torque, especially if you have used too small an easy-out for the
job.

Here are two secrets to removal you will never find in your handyman
book, and are also useful in similar situations.

1)  Upon application of the easy-out, it  will  help if you are careful
to hold your mouth just the right way.  A well known common position,
that seems to be somewhat universal, is the tongue tip in the corner of
the mouth against the upper lip.  You can throw is a bit of head
cocking for additional effect; about 20 degrees is good....

2)  Also a carefully constructed admonishment to the offending screw
about your determination to win, that it had better co-operate or else,
etc. has been found helpful in releasing an otherwise stubborn screw.

Sometimes it necessary to increase the level of threat, adding in a
perfectly syntaxed string of cuss words, until the screw is intimidated
into co-operating.  A real master of this form can cause a stuck screw
to practically unscrew itself.

Tom Lear
San Francisco, CA