The term 'underground music' in my account, connects various forms of music-making that exist largely outside 'mainstream' cultural discourse, such as Drone Metal, Free Improvisation, Power Electronics, and DIY Noise, amongst others. Its connotations of concealment and obscurity indicate what I argue to be the music's central tenets of cultural reclusion, political independence, and aesthetic experiment. In response to a lack of scholarly discussion of this music, my thesis provides a cultural, political, and aesthetic mapping of the underground, whose existence as a coherent entity is being both argued for and 'mapped' here. Outlining the historical context, but focusing on the underground in the digital age, I use a wide range of interdisciplinary research methodologies, including primary interviews, musical analysis, and a critical engagement with various pertinent theoretical sources. In my account, the underground emerges as a marginal, 'antermediated' cultural 'scene' based both on the web and in large urban centres, the latter of whose concentration of resources facilitates the growth of various localised underground scenes. I explore the radical anti-capitalist politics of many underground figures, whilst also examining their financial ties to big business and the state(s). This contradiction is critically explored, with three conclusions being drawn. First, the underground is shown in Part II to be so marginal as to escape, in effect, post-Fordist capitalist subsumption. Second, the practice of 'co-determination' is seen to allow politically engaged underground artists to channel public and private funds into various practices of contestation. Third, and finally, I argue across Part III that in its distinctive musical and iconographic forms, the underground offers a kind of profaning, deforming, sublimating aesthetic 'counter-magic', where radical aesthetic modes and radical practices of representation communicate a kind of 'reconfiguration of the sensible' to audiences. I argue that this 'reconfiguration' might yield emancipatory political readings, whilst also reflecting the kinds of experimental and exploratory musical practices typical in the underground.