This paper presents a brief review of current literature detailing some of the issues and trends in composition and performance with interactive music systems. Of particular interest is how musicians interact with a separate machine entity that exercises agency over the creative process. The use of real-world metaphors as a strategy for increasing audience engagement is also discussed. The composition and system Church Belles is presented, analyzed and evaluated in terms of its architecture, how it relates to existing studies of musician-machine creative interaction and how the use of a real-world metaphor can promote audience perceptions of liveness. This develops previous NIME work by offering a detailed case study of the development process of both a system and a piece for popular, non-improvisational vocal/guitar music.