TC-Helicon VoicePro Instruction Manual page 47

Section 6: Detailed Parameter Descriptions
Insert Path
The compressor can be inserted "Pre EQ" or "Post EQ".
The "Pre EQ" value is useful for targeting compression on
specific frequency bands.
HARMONY | De-ees
Use the Harmony De-esser to help reduce the sibilant
levels associated with homophonic harmony parts.
Amount
Sets the amount that the De-esser will reduce sibilant
levels.
Frequency
Sets the center point of the de-esser detection circuit that
decides when to reduce sibilant sounds.
47