Gearwhistle communicates entirely through mimicry — clicks, whistles, and perfectly replicated phrases — but his craftsmanship speaks loudly enough on its own. The weapons he builds don't miss.
Gearwhistle grew up in a dockside rookery learning to copy the sounds of engines and deals being made. He taught himself smithing by mimicking every motion he watched master craftsmen perform.
He joined the crew after Cid heard him reproduce the exact sound of a broken part and realized he had memorized the noise it should make instead.