Prospective 21e Siècle

French series devoted to electroacoustic and avant-garde music curated by François Bayle and Pierre Henry begun in 1967. It was notable for using on its covers the "Procédé Heliophore" which engraves patterns on aluminum foil that cause optical effects. Some later pressings replaced the foil with standard gray ink. Although the series was French, there are editions of some titles that were released in The Netherlands, England, Spain and Japan. Editions from before 1972 are published by BIEM, after 1972 the rights society was SACEM.