This part introduction presents an overview of the key concepts discussed in the subsequent chapters. The part explores Percy Bysshe Shelley’s complex and creative use of music as an idea and a prosodic device in Prometheus Unbound. It discusses how Shelley experiments with the ways in which to fashion a poetry that begins to behave and affect more like music. The part aims to determine more concisely how and why so many of Shelley’s poems seem “musical” at the same time that music operates as a functional element in the universe of each poem as a whole. It examines how the dialectic between the views of music connects to Shelley’s use of what he calls the “uniform and harmonious recurrence of sound” that is poetic language. The part looks at how Shelley’s prosodic choices inform his use of figurative language, particularly though by no means exclusively, through musical metaphors and other images of sound.