Recorded back in 2006 during that whole period in which Boris and Sunn O))) were also recording Altar, Uroborus Circuit is definitely not what I'd expect from a collaboration between these two musicians. First of all it doesn't have any instruments, which throws out of the window the idea that Atsuo might've contributed drums here; it also doesn't have any sort of recognizable structure aside from the tones overlapping here and there. This is very minimal, consisting on feedback manipulation, hardly resembling guitar feedback due to its subtle, harsh tone, not too different from O'Malley's later works in Table of Elements (Keep An Eye Out).
Download it here: [V0]
Buy it directly from Inoxia Records here.