This book is an attempt to reconsider an area that has become semiotically unknown: musical notation in its twentieth-century developments. This study offers an introductory reflection on the semiotics of notation, which is considered both as a reflection on notation in light of semiotics and a semiotic work that is proper to the notation as such. On the one hand, it is a matter of taking into account the historicity of the phenomenon and the semiotic reflection that has stimulated it; the particular scale of the problem in the period 1950-70 is investigated in relation to causes that could be defined both as "internal" (the changed state of musical matter, serial and post-serial compositional practices, happening and improvisation) and ''external'' (the relationship with other sectors of culture: from visual arts to literature, and to philosophy). On the other hand, the examples considered in the text are a test bench of absolute importance for the observation of the dynamics underlying a semiotically central problem such as that of notation, and of the double order (between the signifier and the signified) that it immediately evokes.