This book investigates the use of extended reality (XR) technologies to innovate the opera experience. Through the creation and comparison of three versions of the original opera Artemis, the research explores how virtual and augmented reality platforms can transform traditional composition and staging practices. The project resulted in three distinct iterations: a virtual reality opera built in Unity3D for the Oculus Quest, a 360° YouTube VR opera, and an augmented reality live performance. Each version utilised self-experiential prototyping to craft immersive environments and novel compositional approaches. Key features of the book include a detailed analysis of prototyping methods for XR opera development, with an emphasis on combining autoethnography, world-building, and user-centric design. By leveraging tools like Unity3D and 3D spatial sound technology, the research demonstrates how XR environments can enhance the sensory and emotional engagement of both creators and audiences. Readers will gain practical insights into designing XR operas, from managing technical constraints to creating immersive soundscapes and environments that align with operatic narratives. This book will appeal to an academic audience in fields such as music technology, interaction design, composition, and virtual reality architecture. It provides valuable contributions for undergraduate and postgraduate students, creative practice researchers, and professionals seeking to explore the intersections of technology, performance, and composition. With its multidisciplinary approach, the book offers a roadmap for applying innovative techniques to the creation of XR operatic works and beyond.