How is tone color changed on the accordion?
An accordion sounds "reedy" because it is a free-reed instrument. However, there are register switches on most accordions, allowing the performer to change between sets of reeds or to allow all to sound. If an accordion has four sets of reeds for the right hand, this is typically depicted as the lower circle in the diagram below. This combination is called the master (or in organ language, "pulling out all the stops". ) It means that one upper set of reeds sounds, two middle sets sound, and one lower set sounds.
By mixing these combinations of four sets, a variety of sounds can be evoked. In the same diagram, from left to right in the top row, it is possible to use only the lower set (often called bassoon), a middle and lower (called bandoneon), a top and bottom and so on. The actual name given to each combination is usually at the discretion of the manufacturer. The next to last register switch on the right would be piccolo, while the final switch, in which NO reeds sound, is used on an electronically-enhanced accordion to mute all reeds and use only electronic sounds.
Similar combinations are found on bass registers. On a full-sized professional accordion, however, there will undoubtedly be five sets of bass reeds , providing a variety of combinations.
Although each set of reeds will produce a "reedy" sound, tasteful combinations (short of using only the master switch on either side) can provide musical results.