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.

The back check is identical with that of the square.

The dampers are the same in their working principles as those of the square, but are generally different in construction; yet, some squares have the same arrangement of dampers as those shown in the cut of the grand action.

The soft pedal of the grand shifts the entire action to the right so that the hammers strike only two and in some cases only one of the strings.

The student should study the three types of actions from the actions themselves, if possible.

[Illustration:  ACTION OF THE GRAND PIANO.]

     ACTION OF THE GRAND PIANO.

    1.  Indicates the felt, cloth or leather, upon which the various
    parts of the action rest, or fall noiselessly.

    2.  Key.

    3.  Bottom; sometimes called Key Rocker.

    4.  Extension; split at lower end to receive center pin in Bottom.

    5.  Wippen Support.

    6.  Jack.

    7.  Jack Spring.

    8.  Flange and Regulating Rail.

    9.  Regulating Screw, Button and Cushion.

    10.  Escapement Lever.

    11.  Regulating Screw in Hammer Flange, for Escapement Lever.

    12.  Check Wire, for Escapement Lever.

    13.  Screw to regulate fall of Escapement Lever.

    14.  Lever Flange, screwed to Flange Rail.

    15.  Hammer Shank.

    16.  Hammer.

    17.  Back Check.

    18.  Damper Lever, leaded.

    19.  Damper Wire, screwed into upright.

    20.  Damper Wire Guide, fastened to Sound-Board.