What happens when a piece of music is written down? What are the conditions of possibility of musical notation? What do we see on a score? Some elements of the analysis of how we write music are offered here in the wake of Peirce’s semiotics. An analogy between musical notation and logical notation indicates that scores are required to be iconic. The three levels of iconicity in music match the trichotomy of hypoicons: if sounds are similar to images, a score is in part a diagrammatic representation of relations and intervals, while musical meaning and emotional interpretant have a metaphorical nature.