Sound device incorporating multiple narrow-band circuits allowing boost and cut of predetermined frequencies. Vertical fader controls are used which provide a ‘graphic' representation of the adjustments across the frequency range. Good for getting rid of feedback.
A means of the adjusting the various frequency bands in audible sound in relation to one another to improve the sound or create special effects. Many have LED displays as well to see the what frequencies are present and their relative strength.
A 3 or 5 band sound control which lets you change volume of separate parts of the sound spectrum to "shape" the sound to your taste.