The hay baler was the most interesting machine on our farm. It had hundreds of moving parts--gears, tines, knives--all rotating at different rates, but intricately coordinated, powered by a single flywheel.
The shearpin was a a safety bolt designed to break--to shear off--when the machinery malfunctioned, causing the flywheel to spin madly fast, harmless, while everything else ground down with a dreadful ticking noise. I remember one occasion in which the cause of the problem was a mystery, and I had to clean the hay out of the main chamber and crawl through it to track down the offending part that had thrown the machine out of balance. The baler was old, greasy, rusted, but years of operation had polished the steel walls mirror-smooth, and the bolt heads were worn round like pebbles in a stream. In this strange intimate place, the baler seemed to possess a will of its own, and I imagined the machine adjusting itself, seeking a state of balance.
In this sound machine, the flywheel is an unchanging, very fast metapulse, from which all of the various tempi and tuplets are derived. The machine approaches the listener, its various processes coordinated. It attempts to shift itself into a high gear, but the strain causes the shearpin to break, wrecking the pulse and disturbing the balance. Gradually the machine rights itself, gathers momentum and continues on its way.