This unprocessed, lawnmower-like, drone was generated on the Roland MKS-80 by modulating a sawtooth waveform with the LFO configured as a sawtooth waveform as well. I found the pitch (a low C) on the keyboard that closely matched the top speed of the LFO then manually swept the tuning of the oscillator by no more than a semitone. This is what created the phasing that can heard throughout the recording.

Sawtooth Modulated Sawtooths