This paper is concerned with the idea that learning to compose music also enables students to think in ways that might be helpful in other contexts. In Britain and elsewhere it has become common to refer to this type of thinking as the 'core' or 'key' skill of critical thinking. Whilst the authors are sceptical about using such reference, they nevertheless argue that there are features of musical composition that are worth learning not only for their own sake but also because they are helpful in learning to think in other curricular contexts. Their small-scale empirical study of classroom practice in Scotland indicates that while this type of learning might be desirable, it is not likely to be realised in contexts in which the emphasis in assessment is on producing a folio of compositions for examination purposes. The authors found that teachers tended not to encourage thinking about the presumed merits of the composition, how merit might be determined and how the composition related to other curricular areas. The study has implications for policy makers and assessment authorities concerned to encourage the development of core or key skills and for teachers and learners who would like to extend their understanding of music into other areas.