A filter is an electronic circuit that allows certain frequencies of an audio signal to pass through while attenuating or blocking others. Filters are an essential component of any modular synthesizer as they allow users to shape the tonal characteristics of a sound and create a wide variety of timbres and textures.
Filters come in various types, but the most common types used in modular synthesizers are the low-pass filter (LPF), high-pass filter (HPF), band-pass filter (BPF), and notch filter. Each filter type has its own characteristics that affect how it modifies the audio signal.
Filters can be combined and modulated in various ways to create more complex and evolving sounds. For example, a low-pass filter can be modulated by an envelope or LFO to create a dynamic filter sweep effect. Filters are an essential tool for shaping the sound of a modular synthesizer, and their versatility allows for a wide range of creative possibilities.