This article analyses two films by Charles Gagnon produced in the late 1960s: The Eighth Day, made for the Christian Pavilion at Expo 67 in Montreal, and The Sound of Space, initially screened in 1969 at the Sixième Biennale in Paris. The study is based primarily on sources that help improve understanding of the production and presentation conditions of these films at the time of their making, thanks to the Charles Gagnon Fonds recently made available to researchers at the National Gallery of Canada’s Library and Archives. More specifically, the text considers the archive’s dual role: on one hand, as an integral part of the form and content of found footage cinema, in which The Eighth Day is included and, on the other hand, as a way of revealing the cinematic materiality in The Sound of Space. The thinking is informed by the theory that the archive renders the material traces of the film visible as much during conception, editing, and recording, as during viewing. The side-by-side examination of these films also makes it possible to highlight that, for Charles Gagnon, the specificity of cinema is determined by both its visual and its sound mediums.