In the generation of its tones, a reed organ is similar to an accordion, but not in its installation, as an accordion is held in both hands whereas a reed organ is usually positioned on the floor in a wooden casing (which might make it mistakable for a piano at the very first glimpse).
Reed organs are operated either with pressure or with suction bellows. Pressure bellows permit a wider range to modify the volume, depending on if the pedalling of the bellows is faster or slower. In North America and the United Kingdom, a reed organ with pressure bellows is referred to as a harmonium, whereas in Europe, any reed organ is called a harmonium regardless of whether it has pressure or suction bellows. As reed organs with pressure bellows were more difficult to produce and therefore more expensive, North American and British reed organs and melodions almost generally use suction bellows and operate on vacuum.
Reed organs of European and U.S. design nearly always have a split keyboard, with one set of stop controls for the bass register at E3 and below and another for the treble.
The standard European configuration of stops included five numbered drawknobs for each register:
U.S.-made reed organs varied considerably in their stop-lists, with the most common instruments having two complete sets of reeds and ten or more drawknobs controlling various couplers and expression features. Larger reed organs were made that had multiple manuals, and in some cases a pedalboard. These were sold primarily as practice organs to professional organists and to churches unable to afford or house a pipe organ.
The reed organ was popular in the late 19th century, replacing the melodeon. The first reed organ was made by François Debain in Paris, France, in 1842 which he called the harmonium. It was used as a practice instrument by organists, most notably César Franck, who composed several collections of works specifically for it, taking advantage of the expressive capacity of varying the bellows pressure using the feet. It was also common in the rural U.S.A., where it was a popular source of home entertainment. It was cheaper than a piano, the tuning was more stable, it was lighter, and it withstood the bumpy shipment by rail better. They were also used in many pioneer churches in the U.S.A., where the reed organ was used for accompaniment of congregational singing instead of a pipe organ.
Advances in piano manufacturing technology in the early 1900s made pianos more affordable, causing reed organs to fall out of favor. Other reasons for the replacement of reed organs were their wavering status somewhere between a sacred pipe organ surrogate and a secular home instrument and the lack of original compositions for reed organs.
A handful of instruments continued to be made until about 1950, some with innovations such as electric blowers; the last US company making reed organs was Esty, which closed down in 1957. Some of the companies also made pianos--Mason & Hamlin, Baldwin, and Steinway, for example--and are still in business. Another, Kimball, made both pianos and reed organs, but has gotten out of the music business entirely; it now makes furniture.
Many reed organs were shipped overseas to support missionary efforts, though they remain common (though often disused) in both private and ecclesiastical ownership. Portable foot-pumped reed organs remained in use in the U.S. armed forces until the end of World War II, where they were used by chaplains to lead worship services aboard ships and in remote locations.
A small number of self-playing reed organs (often called 'organettes') were built in the early 20th century. These used a pin-hole music roll and a pneumatic action as used on player pianos. These often had a much higher number of stops than normal reed organs, since the player's hands were freed from the need to operate the keyboard. This allowed more complex stop arrangements. However, by the time these instruments reached their developmental peak, the market for reed organs in general was starting to decline.
These portable reed organs were brought to India by British missionaries and army chaplains. Indian musicians took them up and incorporated them into their musical life; various companies in India still make reed organs for this market. However, in response to the differences between Indian and Western musical practices, certain changes were made.
Indian music emphasizes melody, rather than harmony; furthermore, Indian musicians prefer to sit on the ground, rather than on chairs. Hence, rather than having the bellows operated by the feet while both hands play on the keyboard, Indian harmonia have bellows on the back operated by one hand while the player picks out he melody on the other. The Indian Harmonium also has a drone stop.
One would think that that accordion or concertina would serve Indian musicians' needs better, but while the British knew the accordion, it wasn't THEIR instrument as it was for either the French or the Germans; hence, few accordions were brought into India by the British, and the Indians were not exposed to that instrument.
Some Indian musicians in immigration, when they could not find reed organs--either Western style or as adapted by Indian manufacturer, have adoped accordions and concertinas.
Reed organs have been largely replaced by electronic organs, but there remain a number of enthusiasts. The finer instruments have a unique tone, and the cabinets of those intended for churches and affluent homes were often excellent pieces of furniture. Several million reed organs and melodians were made in the U.S.A. between the 1850s and the 1920s. Pearl River, a Chinese manufacturer of pianos, accordions, and other musical instruments has started to make reed organs.