Getting to grips with Harrison Birtwistle's ever expanding oeuvre is becoming an increasingly challenging business. The forthcoming South Bank Centre festival naturally provides occasion for some critical stocktaking. Yet the retrospective schemas within which composers' works are traditionally placed seem less than usually appropriate. The idea of linear development is of as limited use to understanding Birtwistle's creative progress as it is to explaining his musical forms. Contrasting musical surfaces, for instance, testify to the difficulty of useful generalization about the recent works' lineage. Whereas the crisp, pulse-based clarity of many pages in The Cry of Anubis bears comparison with moments in Earth Dances and the contemporaneous Words Overheard, Panic's impenetrable textures and sonorities are more reminiscent of the earlier Verses for Ensembles and An Imaginary Landscape. The treatment of musical form in the recent works similarly resists summary description.