The view that music can have a positive or negative effect on a person’s character has been defended throughout the history of philosophy. This paper traces some of the history of the ethos theory and identifies a version of the theory that could be true. This version of the theory can be traced to Plato and Aristotle and was given a clear statement by Herbert Spencer in the nineteenth century. The paper then examines some of the empirical literature on how (...) music can affect dispositions to behave and moral judgement. None of this evidence provides much support for the ethos theory. The paper then proposes a programme of research that has the potential to confirm the ethos theory. (shrink)