Drawing on recent ideas that explore new environments and the changing situations of composition and performance, Simon Emmerson provides a significant contribution to the study of contemporary music, bridging history, aesthetics and the ideas behind evolving performance practices. Whether created in a studio or performed on stage, how does electronic music reflect what is live and living? What is it to perform 'live' in the age of the laptop? Many performer-composers draw upon a 'library' of materials but others refuse to abandon traditionally 'created and structured' electroacoustic work. Lying behind this maelstrom of activity is the perennial relationship to 'theory', that is, ideas, principles and practices that somehow lie behind composers' and performers' actions. The relationship of the body performing to the spaces around has also undergone a revolution as the source of sound production has shifted to the loudspeaker. Emmerson considers these issues in the framework of our increasingly 'acousmatic' world in which we cannot see the source of the sounds we hear.