The stationary parts of the square action are: action frame, to which
is secured the balance rail, balance pins and guide pins, hammer rail,
flange rail, and damper rail. When the key is struck, the parts that
move upward are: the back end of the key, bottom, jack, hammer, back
check, damper wire and damper lever. The hammer falls back upon the
back check immediately after striking, and remains there until the
key is released, when all movable parts fall to rest position.

The action of the jack is the same in all types.


ACTION OF THE GRAND PIANO.

After thoroughly going over the details of the action of the square
and upright pianos, there remains very little to describe in the
action of the grand.

The grand action partakes of the characteristics of both the upright
and the square, and is somewhat more complicated than either.

The bottom and extension are almost identical with those of the
upright; the extension, however, is necessarily very short.

The wippen is of different construction, and somewhat more complicated
in the grand.

The flange rail in the grand is made also to serve the purpose of
regulating rail, as the hammer rail is made to do in the square.