Abstract: This dissertation addresses the role of skepticism in the theory, practice and philosophy of New Music. My aim is twofold: (1) to expose the anti-skeptical background behind the acousmatic reduction and to address its persistence in recent compositional practices; (2) to define a skeptical music in theory and practice, through a philosophical discussion of the productive ways that skepticism critiques intentionality, an analysis of works exhibiting skeptical strategies, and the creation of a new composition informed by these strategies. Part I addresses Pierre Schaeffer's concept of l'objet sonore and its origins in Husserlian phenomenology. Schaeffer reduces the experience of listening to its objective foundations in intentionality, dismissing the significance of history, culture, and context. I argue that the compositional inheritors of Schaeffer's project are the Spectralists. Analyzing Grisey's Partiels, I demonstrate how Spectral composers create musical phenomenological reductions that present listeners with a reduced experience of sounds, ultimately displacing musical skepticism for a non-arbitrary, self-certain grounding to musical composition. Roger Scruton's identification of the 'acousmatic experience' with the 'art of music' inherits Schaeffer's attempt to secure musical practices in the intentional realm. Although formulating a philosophy of music which tacitly accepts the skeptical notion that our relation to the world as such is not one of knowing, Scruton deadens skepticism's force by appealing to the publicity of a common musical language (tonality) and the shared cognitive features of musical understanding (metaphor). Compositionally, Steve Reich's Different Trains repeats Scruton's concerns by resisting the mere literalness of sounds through the transformation of compositional materials into metaphors, appealing to musical conventions and recuperating tonality. In Part II, Wittgenstein's skeptical paradox is invoked to critique the security of the intentional realm, initiating a non-acousmatic theory of listening. This establishes a skeptical project for New Music---the attempt to make our musical 'forms of life' perspicuous. The outlines of a skeptical compositional practice are concretely addressed in two works: Morton Feldman's Piano, Violin, Viola, Cello and Elliott Carter's Night Fantasies . In a final appendix, I discuss the connections between this skeptical practice and my composition of a new work for strings, harp and piano, entitled Anaphora.