A parametric EQ is a type of equalizer having several parameters for control of various filters that can be applied to audio signals. Parametric equalizers are most widely used in situations where very fine control over the audio signal is desired. In order for an equalizer to be parametric it must at least have control over gain, Q, and frequency. In most cases each of these controls are on rotary potentiometers, but there are a few graphic style parametric equalizers on the market.