E-Mu XL-7 Command Station Owner's Manual page 203

A filter which only lets a certain band of frequencies pass is called a
band-pass filter.
100
80
60
40
20
A notch filter is just the opposite of a band-pass filter and is used to
eliminate a narrow band of frequencies.
Another control found on traditional filters is called Q or resonance. A
lowpass filter with a high Q emphasizes the frequencies around the cutoff
frequency. The following chart shows how different amounts of Q affect
the low-pass filter response. In terms of sound, frequencies around the
cutoff tend to "ring" or resonate with high Q settings. If a filter with high Q
is slowly swept back and forth, various overtones are "picked out" of the
sound and amplified as the resonant peak sweeps over them. Bells and
gongs are real world examples of sounds which have a high Q.
Center Frequency
Filter
Output
40 80 160 360 720 1440 2880
Frequency
Low Q Med Q
Frequency
Programming Basics
Dynamic Filters
Band Pass
Filter
...
High Q
XL-7 Owners Manual 191