The VCF section consists of a multimode filter with a 24 dB/oct lowpass, 24 dB/oct highpass, or 12 dB/oct bandpass modes.
If you're not familiar with how voltage-controlled filters operate, a highpass filter (HPF) removes low frequencies as the slider its cutoff slider increased, while a lowpass filter (LPF) removes high frequencies as its cutoff frequency setting is decreased from max, resulting in a dulling of sound. A bandpass filter (BPF) combines both highpass and lowpass curves and allows frequencies "in the middle" to bass.
HPF / BPF/ LPF buttons- These select the current filter curve. Toggling LPF button to select lowpass mode, the HPF button to select highpass mode, or both to select bandpass mode. However, we cannot promise that "bandpass" mode will help your band to pass any auditions. (Cherry Audio: come for the synths, stay for the dad jokes.)
Freq (Frequency)- Sets the frequency where attenuation begins, dependent on currently selected mode.
Res (Resonance)- Emphasizes sound energy at and around the current cutoff frequency by adding feedback from the filter's output back to its input. At lower settings, this can be used to create mild resonances such as those heard in acoustic instruments. When combined with moving the Freq slider, higher Res settings will give the familiar analog synth "wah" sound that launched 1000 disco records.
Env-1 / Env-2 buttons- Allows Envelope 1 or Envelope 2 to modulate cutoff frequency. Use Envelope 1 if you'd like independent envelope control of cutoff frequency; use Envelope 2 if you'd like a single envelope to simultaneously control cutoff frequency and note amplitude. Only one can be enabled at any time.
Env- Sets the amount of cutoff frequency mod via Envelope 1 or Envelope 2 dependent on selection of the buttons above.
LFO-1- Sets the amount of cutoff frequency mod via LFO-1 or Envelope 2 dependent on selection of the buttons above.
Kybd- Commonly known as "keyboard tracking," this causes the cutoff frequency to increase as ascending notes are played on a keyboard. The idea behind this is, because actual note frequencies rise as higher pitches are played, the Kybd slider adds a CV from the keyboard to the cutoff frequency in order to maintain the brightness of notes as higher pitches are played.