Inside the accordion are the reeds that generate the instrument tones. These are organized in different sounding "banks", which can be further combined into "registers" producing differing "timbres". All but the smaller accordions are equipped with switches that control which combination of reed banks operate, organized from high to low registers. Each register stop produces a separate sound timbre, many of which also differ in octaves or in how different octaves are combined. See the accordion reed ranks and switches article for further explanation and audio samples. All but the smallest accordions usually have treble switches. The larger and more expensive accordions often also have bass switches to give options for the reed bank on the bass side.