The harmonium is a keyboard instrument. Thin metal tongues vibrate to a steady current of air produced by pumping the bellows. The harmonium has a three-octave keyboard.Harmoniums reached the height of their popularity in the West in the late 19th and early 20th centuries. They were especially popular in small churches and chapels where a pipe organ would be too large or too expensive; in the funeral-in-absentia scene from Mark Twain’s The Adventures of Tom Sawyer, the protagonist narrates that the church procured a “melodeum” (a conflation, likely intended by Twain for satirical effect, of the names “melodeon” and “harmonium”) for the occasion. Harmoniums generally weigh less than similar sized pianos and are not as easily damaged in transport, thus they were also popular throughout the colonies of the European powers in this period not only because it was easier to ship the instrument out to where it was needed, but it was also easier to transport overland in areas where good-quality roads and railways may have been non-existent. An added attraction of the harmonium in tropical regions was that the instrument held its tune regardless of heat and humidity, unlike the piano. This “export” market was sufficiently lucrative for manufacturers to produce harmoniums with cases impregnated with chemicals to prevent woodworm and other damaging organisms found in the tropics.