What is musical ontology? Why should we as philosophers address it, if ever? These questions constitute the Ariadne's thread running throughout this whole work. The number of papers, volumes and essays that have recently been dedicated to the topic of art and musical ontology is so vast that trying to get a grip on the debate seems like trying to find one's bearings without a compass. This book is a guide to help hapless readers find their way through this philosophical jungle. It is constructed on three levels: the presentation of the debate on musical ontology; a meta-ontological inquiry; and a sort of meta-meta-ontological overview, in which both the ontological and the meta-ontological are examined. It does not contain any apology for musical ontology, nor any attempt to definitively get it off the hook The approach is aporetic, in the spirit of an open investigation in which more questions than answers are posited. But this is the whole point. If this study manages to provide the readers with the necessary theoretical tools to answer these questions for themselves, it could be considered a success. "Whether you are philosophers, musicians or music a cionados, whether you are interested in the analysis, the criticism, the editing, the interpretation of music, or the pursuit of speci c musicological problems, ontology may teach you the kind of issues and considerations to take into account when listening to music. And even if at the end of the book the ontology of art is still not become your cup of tea, I bet the next time you happen upon a performance of My Favorite Things you will dwell for a moment on the puzzles that the sound of music brings about."