Accordion/Reed Ranks and Switches
A reed rank inside an accordion is a full set of the reeds that are used to make different timbres. These reed ranks are located in the reed chamber. Most modern accordions usually have from two to four reed ranks on the right side and three to five on the left side that can be used by themselves or in different combinations to make different types of sounds. They're sometimes classified by the the instruments they imitate, for instance the clarinet, oboe, and bassoon stops. Some more expensive accordions can have up to five or even six different reed ranks on the right side.
The reed ranks can be changed by pressing buttons usually found on the side of the accordion.