Portraits polychromes are a series of books associated with multimedia documents presented on the Internet site of the GRM since 2001. In releasing this collection, our primary concern was to increase awareness of the electroacoustic repertoire and the reserves in the GRM archives. The GRM, being a pioneering centre of electroacoustics, is fortunate to possess a consistent and significant reserve dating back to the beginning of the 1950s. At present, the catalogue contains around 2,000 works, accompanied with supplementary documents: composer's biographies, reviews, photographs, documentary movies, radio broadcasts, recorded public lectures, theoretical research work, transcriptions and analyses. In addition to the heritage value of the GRM's collection, the enterprise of the Portraits polychromes, with the aid of multimedia tools, aims to advance the progress of research on analysis and the transcription of musical works.