A VCF is a Eurorack filter, usually low-pass, whose cutoff can be swept by control voltage

A VCF (Voltage-Controlled Filter) shapes a sound source’s timbre by attenuating frequencies above (low-pass, the most common), below (high-pass) or around (band-pass) a cutoff point. In modular the cutoff and often the resonance are CV-controllable, so an envelope or LFO patched to the cutoff input produces the classic sweeping/plucking movement. Most Eurorack filters are low-pass-only; band- and high-pass on their own are rarer. Because filter character is a matter of taste (how resonance sounds when cranked, whether it distorts pleasantly), the article’s advice is to audition several rather than pick on specs alone.

Examples

Saw VCO -> VCF audio in; ADSR -> VCF cutoff CV: the filter opens and closes with each note for a dynamic pluck. Turn up resonance to emphasise the cutoff frequency, near self-oscillation.

Assessment

Explain what CV-controlling a filter’s cutoff lets you do that a static filter cannot, and name a modulation source you would patch to the cutoff. What does resonance do?