Member of the GRM from 1970 to 1974, Gilles Fresnais participated in the activities of the group headed by François Bayle as Guy Reibel’s Assistant who taught alongside Pierre Schaeffer in the electroacoustic music composition class and musical research at the Conservatoire national de musique in Paris.

In 1971, as a composer Mr. Fresnais actively participated in producing the ‘’Autodafé” opera soundtrack and performances by Maurice Ohana at Lyon Opera under the joint direction of Theodor Guschlbauer and Claire Gibault.

Research Assistant at the GRM, he then worked with Jacques Lejeune on movie soundtracks entrusted to the group in what was called the "cellule de musique pour l’image (‘’music cell for images”).

He was also involved in a recording mission in Bali in 1971. A short film was produced for the occasion and five LPs devoted to the music of this island were released.

A resident of Québec since 1974, he participated as a composer of electroacoustic music in some concerts in Saint-Hyacinthe, Québec and, in 2013, he performed at la Nuit de la création au Musée national des beaux-arts du Québec, as well as at Université Laval (2012 and 2013). Some of his works were broadcast on France Musique in 2013. Despite a few musical activities, he took up composing again in 2010 using new digital audio methods. Vox Aeternam was his first successful piece with this technology. A second piece, Les chants de la terre (Earth Songs), was premiered at Université Laval as part of CRANcert 2014 (Henri-Gagnon hall). Currently, some of its works are broadcast on different radio stations and played in different countries.