I'd like to clarify my previous letter here to say that the degree
of loud pedal compensation was equivalent to subtracting 1/2" sq total
from the spring pneumatic. This is because of the way in which it is
hinged and then connected to the spring pneumatic.
The reason for the compensation was that further study proved that
when the loud pedal was on, the volume of the piano increased slightly,
due to the overall volume increase of the continuously ringing strings.
It's a simple concept. If you graphed the power of a played note with
and without the sustain, the height of the curve in both cases would be
the same, but the decay time of the sustained note would be longer when
the loud pedal is on, so the area under the curve is a little greater
and the tendency of the ear to integrate that effect tells it the note
is louder, rather than equal but of longer duration (equally loud and
I think it is a false premise, since the rolls were not cut
accordingly, at least prior to the modification.