22. High-pass Filters
Another type of filter found in some synthesis systems is the high-pass filter. The high-pass filter functions inversely to the low-pass filter. That is, this filter only passes frequencies above the cutoff frequency while attenuating those below.
Example 22-1: A high-pass filter attenuates frequencies below the cutoff frequency.
It is important to remember that the frequencies input to the high-pass filter that fall below the cutoff frequency are, similar to the low-pass filter, not completely removed, but instead are gradually attenuated.