Q: How important is it to de-ess vocal tracks?
A: Ultimately, the answer depends on how offensive sibilance is in your vocal tracks. If it’s noticeable, then de-essing is a good idea.
De-essers are just what they sound like: processors designed to cut the impact of the highly sibilant “s,” “z,” and “sh” sounds. The process generally uses sidechain compression, gain reduction, and sometimes parametric EQ to reduce the level of sibilant passages without altering the rest of the signal. Universal Audio, Fab Filter, SPL, Waves, and others make excellent de-esser plug-ins.
Having a de-esser in place becomes especially important if you are EQing the vocal to make it brighter or to help it cut through a dense mix; increasing high-frequency EQ will tend to accentuate sibilance, De-essing will bring it back under control.