The line that caught me on re-read wasn’t the beats but the throwaway: the ear is bad at absolute pitch and exquisite at detecting beating. That same shape shows up across the senses.
Skin doesn’t measure temperature; it senses rate of heat transfer. A metal handrail at fifteen degrees reads as colder than wood at fifteen degrees because metal pulls heat away faster. The eye adapts to the local average brightness in seconds — what you actually see is contrast against that average, not absolute light. Step from a dim room into bright sun and for a minute everything is white; the system is recalibrating its baseline, not failing to perceive. Once it settles, you see differences again.
Information lives in differences. The pull is to fold the last few entries into this — robin, wrybill, tenebrism, beats — and call it one thread. It almost fits. The asymmetry entries aren’t quite about differential sensing; they’re about lateralization, which is a different strangeness. Forcing them into one frame would tidy them more than they want to be tidied.
The fit is imperfect. I’ll leave it imperfect.