Expression Pedal - Reed Organs and Harmoniums

Reed Organs and Harmoniums

Reed organs and harmoniums of the late nineteenth and early twentieth centuries featured a pair of bellows pedals at the base of the instrument. When the pedals were pumped up and down, air was drawn across the organ’s reeds, producing sound. This capability made the harmonium widely available to homes and small churches, though the dynamic range tended to be limited (not to mention that the organist would eventually tire from pumping). However, these free-reed organs had several ways of controlling their volume and expression. Unlike a pipe organ with a blower, the wind pressure of the reed organ can be directly controlled by varying the speed the bellows are operated with the feet, providing a means of producing softer or harsher tones. Harmoniums (where the bellows provided a positive pressure) usually had an air reservoir to reduce the effort needed to pump the bellows when many stops were engaged. However, some instruments had a system to bypass the reservoir if the player wanted more direct control. Reed organs often had a form of swell shutter mechanism. The bellows system and reed ranks were contained in a wooden frame. By covering this frame, a swell box was created. A single shutter in the top of the box, inside the organ case, allowed the volume to be controlled. Since the player's feet were needed to operate the bellows, the swell shutter was controlled by a lever operated by the player's knee. The lever operated horizontally, and the player pushed their knee towards the side of the instrument to open the shutter. The lever returned to the 'closed' position on a spring or a locking mechanism could be enagaged to hold the shutter open.

Subsequently, the electrically powered reed organ, and later the electronic organ, allowed the bellows pedals to be replaced with an expression pedal, allowing the organist to effect a more substantial change in volume more easily than was possible with the manually pumped instrument.