Meet Andy Offutt Irwin: Storyteller, humorist, singer, songwriter, musician, whistler and a walking menagerie of sound effects and dialects. The performer, described as equal parts mischievous schoolboy and the Marx Brothers, peppered with a touch of the Southern balladeer, will perform Saturday, Sept. 15, at the Sautee Nacoochee Center. Show time is 8 p.m. Irwin’s stories often feature the adventures of his 85-year-old widowed, newly minted physician and aunt, Dr. Marguerite Van Camp.