An RC filter is designed to prevent certain frequencies from passing through it while allowing others. It is also commonly called a resistor-capacitor circuit or an RC network.
The most basic design of an RC filter is simply a resistor and a capacitor in series. More complex filters add an inductor. RC filters are generally categorized as either "high pass" or "low pass" filters, indicative of which frequencies they filter for. The frequency above or below which all other frequencies are reduced or blocked is called the cutoff frequency. These filters are commonly used in both the playing and studio editing of music.