How does a harmonium work?
The sound of a harmonium is produced by the vibration of reeds, normally made from brass, caused by the release of the flow over them of escaping air when the bellow is pumped. Springs inside the internal bellows often help to facilitate this process. Inside a scale changer harmonium with 3 reeds. Harmoniums are often nowadays made with more than one set of reeds but rarely more than three. The reeds are activated by different stoppers and their function is to add a more rounded sound quality to the thinner sounds produced by single reed pieces. Special drone stoppers produce sound when air is pumped independent of the other reeds. A coupler is sometimes added to the design which when opened permits the player to play the same notes either an octave lower or higher. On most basic harmoniums these are small levers on the right of the keys and on advanced harmoniums small pull out stoppers are attached. The scale changer harmoniums allow the player to transpose a key through 6 full tones
