Stephen McAdams analyses the perceptive process that builds sonic images of the environment. He notes that the listening is in fact more synthetic than analytical, as it is stressed by Helmholtz. Drawing from Gestalt theory, McAdams formulates the concepts of fusion (simultaneous elements are grouped in single identities) and fission (separation of continuous auditory streams), and provides theoretical models of perceptual processes. Fusion responds to three laws: harmonicity, coordinated modulation, and familiarity. Fission depends on numerous factors: asynchronicity in the sound attack, asynchronicity in the coordinated modulations’ attack, and temporal correlation between modulations.