Abstract : The aim of this paper is to elicit "spontaneity" in semi-improvised speech and singing, taking advantage of a comparative study covering two remote forms of expression, namely, improvised dialogues in French and poetry sung by Indian peasant women in Maharashtra. Both are improvisatory processes oriented by predefined topics and constraints. The authors address spontaneous speech / singing production and outline its main features with respect to the forms, functions and actors involved. In this process, they define the role played by subjectivity in prosody and describe its space, indices and contours. Whereas intonation is a globalisation process enacting a cohesion force - both in speech and singing - prosodic excursions in melisms belong to a process of individuation enacting a dissociative force. While acknowledging variability specific to each of these remote forms of communication, the authors attempt to show that prosodic contours in spontaneous speech and in sung poetry display a certain amount of invariance accross languages and speech domains.