In the second,
Cristofori had obtained his escapement with an undivided key,
reconciling his depth of touch, or keyfall, with that of the
contemporary harpsichord, by driving the escapement lever through the
key. He had contrived means for regulating the escapement distance, and
had also invented the last essential of a good pianoforte action, the
check. I will explain what is meant by escapement and check. When, by
a key being put down, the hammer is impelled toward the strings, it is
necessary for their sustained vibration that, after impact, the hammer
should rebound or escape; or it would, as pianoforte makers say,
"block," damping the strings at the moment they should sound.
A dulcimer player gains his elastic blow by the free movement of the
wrist. To gain a similarly elastic blow mechanically in his first
action, Cristofori cut a notch in the butt of his hammer from which the
escapement lever, "linguetta mobile" as he called it--"hopper," as we
call it--being centered at the base, moved forward, when the key was put
down, to the extent of its radius, and after the delivery of the blow
returned to its resting place by the pressure of a spring.
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