Harmoniums are in the family of free-reed aero phones. Each harmonium has bellow at the back that is pumped by one hand while the other hand plays the keyboard. Inside they contain multiple chambers. There are different banks of free reeds in each chamber. The size and shape of each reed in the bank dertermines its pitch. Engaging Stop directs th airflow to various chambers. Each playing key and each Drone controls the air through one or multiple reeds within a chamber. When engaged, Drones provide a continual harmony note and are played in unison with the keyboard. This model has an extra superior quality with three sets of reeds, 5 stops, Bass male and female 3¼”Octaves, French Keys and 7 folds Accordion Type.