A harmonium, also called a “melodeon”, “reed organ” or “pump organ”, is a keyboard instrument. It makes sound by blowing air through reeds, which are tuned to different pitches to make musical notes.
In a hand-pumped harmonium, the player pushes and pulls a handle back and forth with one hand, which is joined to the bellows that blows the air. Because of this, he or she can only use one hand to play the keys as the other must keep pumping the bellows. Air is pumped into an enclosed space by means of bellows. With a keyboard, it is possible to open specially defined holes, through which the pumped air is then pressed. The reeds attached to the openings (double, triple or quadruple reeds) are set vibrating and so produce the desired note.