Bass Accordions -

Pressing one "chord" button actually triggers a combination of three or more reeds internally.

Accordions are categorized by the number of bass buttons they possess, which determines their musical range and weight. Bass Accordions

They typically use multiple ranks of deep reeds (8', 16', and 32') to provide the "foundation" sound for an orchestra, similar to a double bass or tuba. Pressing one "chord" button actually triggers a combination