Laptop composition – the creation and performance of music primarily using laptop computers – emerged as an important musical activity in the last decade of the twentieth century. While much has been written about the cultural and conceptual significance of this new music, less has been published regarding the sonic structure of specific works. This article explores the musical structure and design of compositions by three laptop composers at the turn of the millennium: ‘Untitled #2’ by Oval (Markus Popp), ‘Cow Cow’ by Merzbow (Masami Akita), and ‘Powerbookfiend’ by Kid606 (Miguel De Pedro). Each piece is analysed using spectrographic images, representations of musical sound that allow for the precise measurement of frequency and intensity. Repetition and noise are revealed as musical characteristics common to all three pieces, defining both smaller-scale patterns and large-scale designs. Using the conceptual vocabulary of Paul Virilio and Gilles Deleuze, repetition and noise are framed in relation to a ‘machine aesthetic’ and ‘difference and repetition’.