Audio description is an accessibility service used by blind or visually impaired individuals. Often accompanying movies, television shows, and other visual art forms, the service provides spoken descriptions of visual content, allowing people with vision loss the ability to access information that sighted people obtain visually. At live theatrical events, audio description provides spoken descriptions of scenes, characters, props, and other visual elements that those with vision loss may otherwise find inaccessible. In this paper we present a method for deploying pre-recorded audio description in a live musical theater environment. This method uses a reference recording and an online time warping algorithm to align audio description with live performances, including a process for handling unexpected interruptions. A software implementation that is integrated into an existing theatrical workflow is also described. This system is used in two evaluation experiments that show the method successfully aligns multiple recordings of works of musical theater in order to automatically trigger pre-recorded, descriptive audio in real time.