Retro Synth provides multiple filter types.
A lowpass (LP) filter passes the portion of a signal below a specified cutoff frequency and rolls off the portion above that frequency. A bandpass (BP) filter passes the portion of a signal occupying a band surrounding the cutoff frequency and rolls off the portions above and below that band. A highpass (HP) filter passes the portion of a signal above a specified cutoff frequency and rolls off the portion below that frequency.
There are multiple two-pole, four-pole, multi-pole state-variable and analog-modeled LP, BP, and HP filter designs in Retro Synth, each with distinctive characteristics that you may prefer for a given purpose. The available LP, BP, and HP filter designs include Creamy, Edgy, Gritty, Lush, Lush (Fat), and Sharp variants.
Creamy: Multi-pole state-variable filter.
Edgy: Two- or four-pole analog-modeled filters. Four-pole variants provide a steeper roll-off of frequencies beyond the cutoff.
Gritty: Two-pole filters designed to saturate heavily at higher Resonance and Drive settings.
Lush: Four-pole lowpass analog-modeled filters.
Lush (Fat): Four-pole analog-modeled filters.
Sharp: Two-pole analog-modeled filters.
The three principal filter controls have standard functions for all filter types.
Cutoff: Controls the filter cutoff frequency.
Resonance: Controls the filter resonance or emphasis. Higher settings boost frequencies in the immediate vicinity of the cutoff frequency.
Drive: Allows the filter to be overdriven; the precise effect varies with each filter design.
A band reject filter cuts a narrow band around a resonant frequency. The remainder of the signal is affected minimally.
Cutoff: Sets the frequency of the cut band.
Amount: Controls the amount of attenuation.
A peaking filter boosts a narrow band around a resonant frequency. The remainder of the signal is affected minimally.
Cutoff: Sets the frequency of the boosted band.
Gain: Controls the amount of boost. Higher values are generally the most effective.
BW: Sets the bandwidth around the cutoff frequency.