The idea of high and low sound is fundamental in the development of Western musical writing. Unlike an alphabetical notation, it integrates a strictly visual dimension which is thus attached to the sound, which is however invisible. What is the nature of this resemblance? We obviously rule out the idea of homology, since the audible and the visible are different. The text therefore discusses the two notions of analogy and metaphor, outlining their contexts of use. Analogy is first of all a mathematical notion that governs the analysis of sound. However, the elaboration of the idea of a high or low sound transforms the meaning of the logos that constitutes it. Deciding between metaphor and analogy then becomes a question of the history of ideas and of the conception of the ontology to which the signs relate.