I have a question about the function of the gray knob in the midrange of the Garritan CFX Lite Equalizer (in “Studio View”). There are four dials, as follows, from top to bottom:

1. This knob is blue in color, and is denominated“HI”. It shows a range centered on zero, and allowing 12db adjustment either way, above or below zero.

2. This knob is blue in color and is denominated “MID”. It also has a center position of zero, with 12db range both above and below zero.

3. This is the mystery knob. It is gray in color and is denominated “MID”. It differs from the other “MID” in that its center position is 4KHz, and ranges lower to 500Hz and upwards to 8000Hz.

4. This knob is blue in color and is denominated “LO”. Like knobs 1 and 2 above, its center position is Zero, with ranges of 12 db both below and above zero.

What EXACTLY does knob 3 do?

Does it contract/expand the width of the mid range from a very narrow band of merely 500Hz width, up to a very wide band of 8000Hz? If yes, what is the fixed mid point of that range?

Or,

Is the width of the MID range unchangeable, and, this knob just moves that static width MID band up and down within the overall sound spectrum of approx 20 Hz to 20,000Hz? If yes, what is the width of the moveable MID range?

Or, does it do something else that I have not thought of?

Thanks for you help!