Granulations-Sillages develops an idea glimpsed at in Franges du Signe: the existence of extreme times, at the edge of our faculties of perception, which only the electroacoustic music tools allow us to realise. Two natures of phenomena, opposed in all respects (the Granulations-Trails and the Tutti), alternate through seven movements that constitute the piece.  The work is designed for six channels diffused in concert on a main stereo system facing the public and two auxiliary stereos (group of crossing speakers: front-back and left-right in the room). 

Franges du Signe, the third part of an electroacoustic triptych completed in 1973-1974, is the first major "purely acousmatic" work composed by Guy Reibel. Franges du Signe explores the mathematical idea of the limit by translating it musically, searching for unstable states of equilibrium.
Thus, several conflicting tendencies or logics act upon the sounds. They overlap and fight, each one seeking to assert its trace on the phenomenon in progress, generating de facto an ambiguity that is unique to all phenomena that obey the "logic of the living". 

Guy Reibel (born 1936) started out with a double qualification; he first became an engineer and then studied composition in Paris with Olivier Messiaen, teacher of Karlheinz Stockhausen, Iannis Xenakis, François Bayle, to name just a few. Pierre Schaeffer, the director of the Groupe de Recherches Musicales (GRM), soon offered him a chance to edit and work out the famous 1967 Solfège de L'Objet Sonore three-LP box (the practical part of his theoretical manifest Traité des objets musicaux), and to codirect the class for electroacoustic music at the National Music Conservatory. During that period Reibel worked intensively in the studios of the GRM. Not only did he compose some milestones of electronic music, he also developed a very music-based theory of electronic music, implementing ideas of musical gesture and game theory -- in the '60s, long before anyone else discussed those issues. Conflicts with other members of the GRM led to Reibel's departure from the group (though he had been considered Schaeffer's successor as director), and Reibel toured the world as conductor of his newly-founded Groupe Vocale de France (who realized the first complete recording of Ligeti's choir work) and took over a director's position at Radio France.