Harmonium is a small and portable hand-pumped reed organ which is very popular in the Indian subcontinent. Reed-organs arrived in India during the mid-19th century, possibly with missionaries or traders. Over time they were modified by Indian craftsmen to be played on the floor, and to be smaller and more portable. 

The basic components of an Indian harmonium include: a wooden body with two metal handles for carrying, banks of brass reeds (often 1, 2, or 3) set on a wooden reed board, a pumping apparatus (bellows), air stops (including stops for drones), and a keyboard (which is similar to a piano keyboard but with a smaller number of keys). The sound is produced by the air, which is pumped by the bellows into an internal reservoir bellows inside the harmonium. Air from this inner reservoir escapes to vibrate the reeds. This allows for a continuously sustained sound.