A melodeon (also known as a cabinet organ or American organ) is a type of 19th century reed organ with a foot-operated vacuumbellows, and a pianokeyboard. It differs from the related harmonium, which uses a pressure bellows. Melodeons were manufactured in the United States sometime after 1812 until the Civil War era. By 1840 forty builders are listed.
While it was sometimes used as a substitute for the pipe organ in small churches, it was primarily used in domestic settings.
In Ireland, the word is found in the commonly used phrase "cat melodeon". This simply means that something is awful. For example, if it is raining, one might say that the weather is "cat melodeon". The etymology of the phrase is uncertain, but may analogize poorly-played melodion music to the sound of a cat in heat.