External feedback loop allows a wide range of sound modification devices to be inserted in the MF-104's feedback loop. Output jacks include Mix Out, Delay Out, and Loop Out. Rugged hardwood and black-enameled steel enclosure with solid, authentic vintage synthesizer knobs and switches. Control parameters are signal mix, cutoff frequency, resonance amount, and envelope amount. All of the Lowpass Filter's parameters can be controlled with expression pedals or external control voltages as well as by rotary panel controls.
Panel switches select filter mode and envelope follower response speed.
The moogerfooger Ring Modulator multiplies an audio input and a carrier oscillator to produce sum and difference frequencies. Panel switches select carrier oscillator range and LFO waveform. The moogerfooger CP-251 Control Processor is a collection of classic basic circuits for generating, modifying, combining, and distributing control signals. Both inverting and non-inverting outputs are present. Controls include two input attenuators, master gain, and offset level.