the.com/bugle call

means A short, specific melody played on a bugle to signal soldiers to do something — wake up, eat, gather, or sleep — without needing written orders.

from 'Bugle' traces back to the Latin 'buculus,' a young bull, because the earliest bugles were literally hollowed-out ox or cow horns used as hunting signal-horns. The instrument kept the name even after it became metal, and the military adopted its clear, far-carrying tone for exactly the job animal horns had always done: broadcasting a command across a distance no voice could cover.