The black Moogerfooger MF-101 Low-Pass Filter from Moog is a tabletop- or pedalboard-operable voltage-controlled low-pass filter for both line- and instrument-level sources. It can be used for synths, guitar, and bass as well as recorded sources. The MF-101 features an adjustable envelope follower that produces a control voltage based on the dynamics of its input, creating a higher voltage the harder you play.
The low-pass filter itself has a selectable cutoff frequency between 20Hz and 12kHz, and the adjustable resonance allows you to dictate whether you want the frequencies near the cutoff to be boosted, and by how much. You can set the filter's frequency response for bright or dark by selecting between 2- or 4-pole operation. The mix knob allows you to set the wet/dry rate, while 1/4" inputs for cutoff, mix, resonance, and amount allow you to integrate an expression pedal for further control and manipulation of your sound.