This book re-examines how Bonhoeffer employs musical patterns of thought and language to a theological end. It outlines how the significance of Bonhoeffer's musico-theology has not been sufficiently recognised, and sets the stage for a rigorous re-examination. It becomes clear that through the lens of his musical metaphor of polyphony, Bonhoeffer demonstrates how his account of Christian formation contains a latent pneumatology. Tarassenko demonstrates that incorporation of this pneumatology is key in deepening one's understanding of Bonhoeffer. It allows the relationship between Christology and Christian formation in Bonhoeffer's thought to become fully realised. The appeal to polyphony articulates this pneumatology, as an indirect but nevertheless exceedingly successful means of contouring an account of the Spirit's work.