FILTER

A circuit that attenuates or removes frequencies from a sound or waveform above or below a certain frequency. Filters can be used to reduce unwanted noise above or below the frequency range of a voice or instrument. One type of filter, a bandpass filter, allows the frequencies within a specified range to pass, while a notch filter inhibits the frequencies in a specified range. Even MIDI data can be filtered, using a MIDI data filter, to remove specified messages (pitch bend, modulation) from the MIDI data stream.