I have heard of the harmonium. As described in an article I found on the internet, this is essentially what my wife owns. It's a reed organ. It stands upright like a small piano, and the air to operate the reeds is produced by pumping pedals. It's portable and can be collapsed into a box about the size of a foot locker. Similar to, but not exactly like, THIS. These instruments were very popular in small frontier churches and at traveling tent meetings. Barbara says she has never heard it referred to as anything but a "portable reed organ" or a "camp organ."

Genealogy:

The harmonium was invented in Paris in 1842 by Alexandre Debain, though there was concurrent development of similar instruments. Christian Gottlieb Kratzenstein (1723-1795), Professor of Physiology at Copenhagen, was credited with the first free reed to be made in the western world after winning the annual prize in 1780 from the Imperial Academy of St.Petersburg.

I've never heard of it referred to as an "American reed organ." Maybe it's an English thing. . . .

Don Firth