While I'm only a beginner, it sounds to me like there's a bit of layering going on there. I think there are multiple sawtooth oscillators in unison, one with a short envelope and delay effect and another sustained as a pad/drone with a sub overtone and a fair amount of chorus/reverb effect.
I was able to achieve something like this with another external monosynth patched via the pitch and gate output and back into the audio input. The external synth was set for a short envelope sawtooth with some LP filtering, and the brute was set with a triangle with some metalizer and sub overtones and set for maximum sustain and release on the envelope. I connected the brute headphone out to some cheap delay and reverb effects pedals (the delay was set to a short time with "analog" style feedback, the reverb was set to a long "hall" type). I played notes "G" and "F" from octave "-1". With enough tweaking of the filter, brute factor and delay I think it sounded pretty similar.