A displacement amount detecting apparatus is provided and includes: transmission member, transmitting a displacement on one end side thereof to a displacement on the other end side thereof; a sensor, disposed to face the other end side of the transmission member, and configured to output a value according to a distance between the sensor and the other end side of the transmission member; a calculation device, calculating a value for indicating the distance based on the value output by the sensor and a reference value; and a correction device, correcting the reference value. When the one end side is displaced in a first direction, the other end side is displaced in a second direction opposite to the first direction and away from the sensor. The correction) device is configured to correct the reference value based on the value for indicating the distance calculated by the calculation device.

A displacement amount detecting apparatus is provided and includes: transmission member, transmitting a displacement on one end side thereof to a displacement on the other end side thereof; a sensor, disposed to face the other end side of the transmission member, and configured to output a value according to a distance between the sensor and the other end side of the transmission member; a calculation device, calculating a value for indicating the distance based on the value output by the sensor and a reference value; and a correction device, correcting the reference value. When the one end side is displaced in a first direction, the other end side is displaced in a second direction opposite to the first direction and away from the sensor. The correction device is configured to correct the reference value based on the value for indicating the distance calculated by the calculation device.

A chromatic harmonica with reduced air leakage in which a flexible mouthpiece replaces the conventional rigid mouthpiece, and a low friction valve slide replaces the conventional valve slide, thereby allowing the low friction valve slide to move horizontally when played without binding, and which eliminates the need for a gap between the mouthpiece and valve slide through which air leaks. For the chromatic harmonica with a flexible mouthpiece to function properly, a new button configuration is added. The button is disposed in the rear portion of the chromatic harmonica. A bar is attached to the button at one end of the bar, and the other end of the bar inserts into an opening in the valve slide. The button further comprises a cylinder, around which a spring is disposed. The cylinder inserts inside of a hole on a side of the chromatic harmonica adjacent the rear.