The big red barn at the Center for Performing Arts in Rhinebeck is just shy of 20 years old (though it could pass for a historic Dutch barn). In two decades, the barn has has seen a lot of action—2,000 different productions, 16,000 artists, 300,000 patrons, and 2,500 students. The nonprofit is an important community venue and a high-caliber resource for hands-on technical and performance training in all aspects of theater arts. In October, the Rhinebeck Theatre Society will stage “Dark of the Moon,” a haunting Smokey Mountain drama with a bluegrass score, and “CLUE! The Musical,” which brings everyone’s favorite murder mystery game to life for an interactive show.