A harmonium is a free-standing keyboard instrument similar to a reed organ. Sound is produced by air, supplied by foot-operated or hand-operated bellows, being blown through sets of free reeds, resulting in a sound similar to that of an accordion.

Definition

In North America, the most common pedal-pumped free reed keyboard instrument is known as the American Reed Organ, (or parlor organ, pump organ, cabinet organ, cottage organ, etc.) and along with the earlier melodeon, is operated by a suction bellows where air is sucked through the reeds to produce the sound. A reed organ with a pressure bellows, that pushes the air through the reeds, is referred to as a harmonium.

In much of Europe, the term "harmonium" is used to describe all pedal pumped keyboard free reed instruments, making no distinction whether it has a pressure or suction bellows. The British introduced harmoniums to North India during the colonial period.