The author discusses the use of sound analysis as a compositional tool for music synthesis. The first part is an introduction to analysis, synthesis and representation of sounds from antiquity to the first digital synthesis in the mid-1950s. The second part describes the method of timbral synthesis by analysis. In the third part, the author presents some synthesis examples from his works and works by other composers. The following two parts concern the possibilities of automatically identifying parameters within the sound and the various models of analysis-synthesis. The final part examines the representation of sound as a compositional tool.