
"Reznor used his roomful of instruments—a vacuum-tube-powered drum machine [], a Casio SK-1 keyboard with a bent circuit board, and so on—to put together a library of analog and electronic beats... Building on top of this substructure, Reznor and Ross spent two days recording ancillary melodies on a Moog Minimoog Voyager [], an out-of-tune African marimba, a ukulele [], and other instruments." via Antony.