Despite the gradual proliferation of scholarly work around sound, and in particular its role in experimental music, there is little explicitly sonic philosophy that attempts to provide a ground for such research. Decades after the work of Pierre Schaeffer to theorise the objet sonore – sound object – and John Cage’s (1973: 10) call to ‘let sounds be themselves’, there remain few ontological and epistemological frameworks to support investigations into aesthetic, ethical and political questions related to experimental music practice and the place of sound in it. This makes writing about sound difficult and contributes to a lack of clarity or specificity in the use of terms such as ‘sound’, ‘noise’ and ‘silence’. In this article I seek to address this, connecting the work of transcendentalist Henry David Thoreau, experimental music composer and thinker Cage and philosopher Michel Serres with my own experience to develop an account of sound in experimental music that approaches it as multiplicity. This allows sound to be heard as physical, perceptual and conceptual and brings into question the reproducibility of sound, emphasising the place of sound as part of its environment.