PURPOSE: To prevent the transmission of a reaction to the finger of a player at pressing, and prevent bouncing by providing a pressing force transmitting member, a thin member, and a small hole for releasing the air in a semi-closed space.

CONSTITUTION: When a keyboard is pressed by a player, and the upper surface of a cylindrical part 12 is pressed by an actuator 20, an elastic part 14 is pressed and deformed to bring a movable contact 8 into contact with a fixed contact 4. When it is further pressed, a thin part 18 for supporting the contact 8 is also deformed. Since the air pressure in an upper chamber 22 which forms a semi-closed space when the contact 8 makes contact with the contact 4 becomes higher than the air pressure in a lower chamber 24, a contact support part 16 is pressed onto the contact 4. Thus, no bouncing between the contacts is caused by the air spring function of the chamber 22. As the reaction from the support part 6 added to the part 16 is absorbed by the deformation of the part 18, it is never transmitted to the finger of the player. Further, since the air in the chamber 22 is released to the outside through a small hole 26, the air spring function never give the reaction, and bouncing can be thus prevented.