via Rich Decibels where you'll find additional details.
"Here’s something I made for the Concerned Citizens exhibition opening this weekend in Wellington"
"This particular piece is a one-off that is being auctioned to raise funds for the victims of the preposterous “anti-terror” raids of 2007 (more details at the Concerned Citizens and October 15 Solidarity websites)...
It’s a bass drone synth with two pairs of heterodyning oscillators. Here’s what it sounds like with some reverb and filtering added:"
Rich Decibels Drone Explosion with EHX Memory Man by Rich Decibels