The HMF tab provides controls for the high mid frequency band of the EQ. This band is a peak EQ.
The Frequency control lets you set the center frequency for the peak high mid frequency band.
The Gain control lets you boost or attenuate the corresponding frequencies for the high mid frequency band.
The Q control changes the width of the high mid peak EQ band. Higher Q values represent narrower bandwidths. Lower Q values represent wider bandwidths.