A type of tonal control or equalization tool used in sound systems. They have a group of sliders for boosting and cutting specific frequencies, or groups of frequencies. A common graphic equalizer is the 31 band graphic equalizer that has 31 separate frequency controls ranging from 20 Hz to 20 KHz. They are often referred to as 1/3-octave eq’s because each slider is spaced one third of an octave from its adjacent frequencies. A common practice is modern sound systems is to have a third octave eq on each of your main speaker sends as well as your monitor sends. They are especially useful on stage monitor sends to aid in the specific cutting of frequencies before they cause feedback.