Harmonium

Harmonium, a musical instrument of the "free reed" class. In the harmonium the air is compressed by bellows and escapes through the reeds, whereas in the American organ - the other type of reed-organ - the bellows cause a vacuum into which the reeds admit the outside air. The reeds or "vibrators" are constructed in the following manner. Narrow rectangular slits cut in a piece of brass-plate are covered with tongues of brass, one end of which is attached to the plate, the other remaining free. The current of air which moves the reeds and thereby produces the musical tone is admitted into the wind-chest in which the reeds are placed through valves below or above the keys in the key-board. The pressure of wind arises through the action of bellows which the player controls by moving the treadles alternately with his feet, thereby pressing down the keys and opening the valves so as to allow the wind to pass from the bellows to the wind-chest. The pitch is not regulated by the force of the pressure, but by the length and elasticity of the reeds, and by the shape and capacity of the channels or air-chambers above each reed. The key-board has a compass of five octaves, from c to C. The first successful harmonium was made by Dehain, of Paris, in 1840. By the melody attachment, invented in 1864, stress is given to one or more notes in the upper peirt of the harmony by shutting off all the lower ones. The best harmoniums are now made in Paris. The cheapness of the instrument, and the ease with which it can be played, render it a useful substitute for the organ.