The first in-depth historical overview of spectral music, which is widely regarded, alongside minimalism, as one of the two most influential compositional movements of the last fifty years. Charting spectral music's development in France from 1972 to 1982, this ground-breaking study establishes how spectral music's innovations combined existing techniques from post-war music with the use of information technology. The first section focuses on Gérard Grisey, showing how he creatively developed techniques from Messiaen, Xenakis, Ligeti, Stockhausen and Boulez towards a distinctive style of music based on groups of sounds mutating in time. The second section shows how a wider generation of young composers centred on the Parisian collective L'Itinéraire developed a common vision of music embracing seismic developments in in psychoacoustics and computer sound synthesis. Framed against institutional and political developments in France, spectral music is shown as at once an inventive artistic response to the information age and a continuation of the French colouristic tradition.