In response to Suzanne Cusick's anti-dualist injunction, this chapter is based on 'theory', reading Gilles Deleuze's musical thought through his philosophical relation to seventeenth-century Dutch philosopher Baruch Spinoza, one of the earliest critics of dualist paradigm for mind/body relatedness. It examines a narrative in the history of ideas in which music studies find the resolution of the mind/body problem already at work. The chapter discusses how Deleuze's Spinozistic philosophical position lends the materiality of musical sound and the bodies that produce and experience it an ethical orientation. By situating Deleuze's musical thought squarely within Spinoza's philosophy, the chapter details the ontological bases for the construal of mind/body relations upon which Deleuze predicates music's ethical potential. The Ethics, the text with which the chapter is engaged, as the definitive articulation of Spinoza's ontology, appears posthumously in 1677. In the passage from Practical Philosophy with which the chapter explores that, Deleuze refers to the constitutive units of musical forms as 'sound particles'.