A split in the sound board, in any style of piano, sometimes causes trouble due to the vibrating edges of the board coming in contact with each other.  Insert the point of your screwdriver in the crack, holding it there firmly; if the rattling stops, the difficulty is discovered, and may be remedied by placing a screw or wedge in the crack, or a wedge of wood, cork or rubber between the sound board and iron plate or casing, if the location of the trouble permits.  While this method seems a perfunctory one, it is nevertheless the best the tuner is prepared to do, for it is next to impossible to glue a crack in the sound board successfully outside of a regular factory or repair shop, where the instrument may be taken all apart and a new sound board put in or the old one properly repaired.

Sometimes the sound board gets loose or unglued at the edges, or the bridges or ribs come loose.  Any part of the piano where there is vibration or loose material may become the source of the sympathetic rattle, as even parts of the case vibrate with the tones struck; so you must examine the panels, lock, hinges, soft pedal bar (in square), in fact all parts of the case and woodwork for the location of the trouble.  Once found, the remedy will suggest itself.  The greatest difficulty is to locate the cause.  Very frequently this will be found entirely outside of the piano; a loose window glass, picture glass, lamp or other article of furniture in the room may respond to a particular tone or its octave.  We have never found the sympathetic rattle in the action; it has rattles, but not of this character.  Any other defect which may be found under this head will only require the exercise of a little mechanical ingenuity to suggest a remedy.

REGULATING AND REPAIRING THE UPRIGHT ACTION.

(Use cut of upright action for reference in following study.)

We will begin with the key and take up each part of the action in the succession in which motion is transmitted.

1. Key.—­Keys stick; that is, after being struck, they fail to come up quickly, if at all.  First ascertain if the trouble is really in the key, or in the upper part of the action.  To do this, lift the extension or wippen until the upper part of the action is entirely free from the key, so that you may test the key independently.  Some keys are leaded so that they will fall in front of the balance rail, others so that they will fall back of it; in either case, lift the low end and let go, to see if it will fall by its own weight.  If it seems quite free, you may know the trouble is not in the key; you will also find that when you release the extension or wippen, it will not fall readily, showing that the trouble lies in the upper part.

If the trouble is found in the key, examine the guide pin.  See if it is placed in a direct line with the key.  If so, and it still binds, enlarge the hole by pressing the wood back slightly with some wedge-shaped instrument, if you have not a pair of the key pliers which are used for this purpose.  See that the cloth, with which the hole is bushed, is not loose and wrinkled.  Do not oil or grease the guide pin unless such treatment has been previously resorted to, as the polished pin will work more freely in the dry cloth.  Do not pinch hard on the pin with rough pliers and spoil the polished surface.