The Start of the Chain Reaction
When the key is depressed by the pianist, it sets the action in motion, beginning the complex chain reaction that ends with the hammer striking the string. The key (1) rests on a series of rails that are glued to the top of the keyframe (2). The front rail (3) runs across the front of the keyframe and supports the front end of the key. The front of the key is held in place by the front rail pin (4), a small metal pin which protrudes from the front rail (this pin may also be called the batt pin). The pin fits into a felt-lined hole in the bottom of the key. A felt pad, called the front rail punching (5), cushions the bottom of the key as it is pressed down, ensuring silent operation. The key pivots on the balance rail (6), and is held in position on the rail by the balance rail pin (7). The balance rail pin fits in a felt-lined hole in the middle of the key, and the contact point between the key and the balance rail is padded by the balance rail punching (8). The back end of the key rests on a pad called the key rest felt (9). The visible portion of the key – the key top (10) and key front (11) are covered with a special plastic.
When the key is depressed by the pianist, it pivots like a see-saw on the balance rail. The capstan (12), a screw attached to the back
portion of the key, pushes up on the wippen heel, which sets the
action into motion. The height of the capstan can be adjusted in order to make sure that it comes into solid contact with the wippen. The damper lift felt (13) is found on the very back of the key. When
the key is depressed, this felt pad catches the bottom of the damper level, raising the damper assembly from the string. The back check (14) is attached to the back of the key by the back check
wire (15). The back check is a small leather-covered wooden block which catches the tail of the hammer as it rebounds from the
string. Small lead weights, which are referred to simply as leads (16), are inserted in the front of the key to balance the weight of the
action. Without the leads, the pianist would have to exert more pressure on the key in order to lift the weight of the action. With the leads, the pianist is required to
exert less than two ounces of downward pressure to sound a note.
Follow the link to see the key in action…