Despite traditionally having been studied within the field of Musicology, the analysis of music in film should be approached as an aesthetic study of the relationship between «image» and «music» which is central to the cinematographic framework. From this interdisciplinary perspective numerous theoretical and methodological issues emerge. The aim of this article is to investigate, using both a synchronic and diachronic focus, some of the key issues arising from this joint music-image approach, in an attempt to develop a theoretical framework for a joint aesthetic of music and image: a study of «cinematographic expression» that brings together the visual and the sound dimensions and which we call the «musicalised image», a neologism of our own creation.