How do you desensitize a horse to crowds, noise, and the show environment?

The show environment combines stimuli that individually might not concern a well-prepared horse but that together — crowd noise, loudspeaker announcements, flags, other horses, unfamiliar footing, different smells — create a cumulative activation level that exceeds many horses' normal tolerance threshold. Clinton Anderson, Pat Parelli, and Warwick Schiller all address show environment preparation as a specific training goal distinct from general desensitization. Anderson's approach is to take the horse to show environments before it needs to perform there — hauling to a showground when no show is happening, standing near the warm-up area while other horses work, parking near the announcer booth while it is active. Each exposure is treated as a desensitization session: the horse is allowed to process the environment, and the handler or rider works through whatever response the horse shows rather than trying to suppress it. He specifically recommends attending smaller, less intense shows first before major events, allowing the horse to build its show environment tolerance progressively rather than expecting it to handle its first show at the highest intensity level it will ever encounter. Warwick Schiller's contribution is identifying that show environment anxiety is often primarily social in origin — the horse is away from its herd in an unfamiliar place with unfamiliar horses, and its nervous system activation is driven by the herd separation as much as by the environmental stimuli. His approach of building genuine secure attachment with the handler is particularly relevant here: a horse that has a genuine safe base relationship with its rider will regulate its show environment anxiety through the rider's presence more effectively than a horse that is merely well trained.