Repetition, as a component of musical structure in popular songs, has long played an important part in ‘popular common-sense’ definitions, and criticisms, of the music. ‘It's monotonous’; ‘it's all the same’; ‘it's predictable’: such reactions have probably filtered down from the discussions of mass culture theorists. From this point of view, repetition (within a song) can be assimilated to the same category as what Adorno termed standardisation (as between songs). Of course, the significance of the role played by such techniques in the operations of the music industry – their efficacy in helping to define and hold markets, to channel types of consumption, to pre-form response and to make listening easy – can hardly be denied; it is, however, equally difficult to reduce the function of repetition simply to an analysis of the ‘political economy’ of popular music production and its ideological effects. Despite Adorno's critical assault (see Adorno 1941), despite later twists to the theory by, for instance, Fredric Jameson (1981), who argues that rather than being a negative quality of mass culture, repetition is simply a fundamental characteristic of all cultural production under contemporary capitalism, the question of repetition refuses to go away. Why do listeners find interest and pleasure in hearing the same thing over again? To be able to answer this question, which has troubled not only mass cultural theory but also traditional philosophical aesthetics, as well as more recent approaches such as psychoanalysis and information theory, would tell us more about the nature of popular music, and hence, mutatis mutandis, about music in general, than almost anything else. We must start by locating repetition within an overall theory of musical syntax.