Equalization is the process that engineers use to alter the frequency response of an audio signal. Frequencies become more pronounced (if boosting) or less pronounced (if cutting), depending on what the engineer is trying to accomplish. Equalization (or EQ) is a crucial tool used in all phases of music production. Whether to enhance or minimize some aspect of the frequency spectrum, EQ is an important part of the workflow for the recording professional. In this chapter, we will take a look at the beginnings of equalization and take a detailed look at the practical applications of EQ in your workflow.