STORY SUBMITTED For many of them, it started with doubt. A 20-year-old from Brookhaven who thought the invitation had to be a joke. A shy teenager who had only ever sung alone. A young woman who joined the choir simply because a persistent friend wouldn’t take no for an answer. But on Memorial Day weekend, 24 from Copiah-Lincoln Community College stood on one of the most storied stages in the world — Carnegie Hall — and performed a world premier…