Gamelan is a State Military Officer serving with the Third Sovereign Battalion in Central City. He's exclusive to the 2009 anime—the manga uses a different character, Storch, in his place.
His main moment comes in Episode 56 when he and his platoon are sent to back up Führer King Bradley. They're tasked with retaking the main gate of Central Command headquarters from Fort Briggs soldiers, but things don't go well. Fu shows up and takes out Gamelan and his entire platoon in a single attack, leaving them all unconscious.
His name may be inspired by Maurice Gamelin, the French military commander-in-chief during the early stages of World War II, though this remains speculative.
Content compiled by AnimeList.moe from publicly available sources.