De-essing is also known as "frequency dependent compression," but whatever you call it, the idea is to control excessive sibilance (exaggerated "s" sounds), which can be particularly problematic on vocal tracks. The multiband capability is a feature that puts the De-Esser ahead of the competition making it precise and versatile on top of good sounding.
When set as 2 band mode the De-Esser works in a broader fashion, effectively reducing the high end content of the area set by the frequency selector. Switching to 3 bands mode allows more precision and control, particularly useful in situations like vocal tracks where sibilance is in a narrow range, and where there is the need to leave the higher part "air" untouched. The dedicated control set also allows you to precisely tailor the operating mode, and audition the de-essing action or the part of the audio spectrum the processor is working on.
The Custom Shop: