Beware of long books with short titles. The Politics of Opera looks straightforward enough, especially when the subtitle reveals that the period it covers is confined to the 17th and 18th centuries. But the amber light is triggered at once by an introduction entitled ‘Prologue: Mixtures, Boundaries, Parallels’, a mystifying triad left unexplained by what follows. What does appear is a supporting cast of non-musicians, including Machiavelli, Descartes, Hegel, Collingwood and Quentin Skinner, and an admission that the author is not a musicologist or a historian but ‘a student of political thought’. The most important of the intellectuals cited turns out to be Skinner, a historian of ideas. Connoisseurs of the school associated with him will know what to expect, although Cohen does not fully acknowledge his debt to Skinner until the very end of the book, in an appendix labelled ‘Backstage’. This should be read immediately after the introduction if the book is to make sense. He tells us there that he has ‘tried to avoid or correct my own interpretive conceits throughout the book by means of a constantly changing methodological medley’, but in reality there is just one dominant melody: the contextualisation associated with what was once called the ‘Cambridge school’.