As discussed in the video, this unit was used by many famous artists, producers and engineers in the late 90s and early 00s across a broad range of styles. The Mutator is a stereo pair of analogue, resonant low pass filters (SSM 2045s) and voltage controlled amplifiers that are contoured by envelope followers and/or LFOs. In a nutshell, that allows for all sorts of stereo filtering, sweeping and tremolo FX on an open-ended number of audio sources. There is further functionality such as additional attack and release times, external inputs for creating alternate envelopes, external CV ins, LFO linking/inverting, MIDI control and MIDI LFO reset etc. Most (but not all) of this was used at some point in the video.