They called it frogging: pulling the yarn back off the stick, because it goes rrrribbit, rrrribbit.
Turned up, the low part of every pull is a deep, round rumble you feel as much as hear. The higher bits sound like a DJ scratching vinyl.
No two pulls sounded the same. This take is my favorite: one shot, no cuts, and right as the loops let go you can see a little cloud of yarn dust. At the end, that moment plays again at half speed, one octave lower.