Reed or pump organ
. Operation of the two large pedals at the bottom of the case supplies wind to the reeds.
The pump organ, reed organ or harmonium, was the other main type of organ before the development of the electronic organ. It generated its sounds using reeds similar to those of a piano accordion. Smaller, cheaper and more portable than the corresponding pipe instrument, these were widely used in smaller churches and in private homes, but their volume and tonal range was extremely limited. They were generally limited to one or two manuals; they seldom had a pedalboard.
- Harmonium or parlor organ: a reed instrument, usually with several stops and two foot-operated bellows.
- American reed organ: similar to the Harmonium, but that works on negative pressure, sucking air through the reeds.
- Melodeon: a reed instrument with an air reservoir and a foot operated bellows. It was popular in the US in the mid-19th century. (This should not to be confused with the diatonic button accordion which is also known as the melodeon.)
The chord organ was invented by Laurens Hammond in 1950. It provided chord buttons for the left hand, similar to an accordion. Other reed organ manufacturers have also produced chord organs, most notably Magnus from 1958 to the late 1970s.