The Four Seasons and the rest of the concertos in Op. 8 represent Vivaldi's remarkable innovation in the field of the Baroque concerto. This detailed guide examines the work's origin and construction in a way that enables the reader to distinguish what is extraordinary about the Seasons and what constitutes the composer's customary method of 'characterising' the solo concerto. Drawing on recent research and his own expertise in the appraisal of Vivaldi's manuscripts, the author draws new and sometimes startling conclusions about the conception of the Seasons, the origin of their programme, the dating of the concertos and the rationale behind the collection's ritornello-form structures and aria-like slow movements. The significance of Vivaldi's idiosyncratic art is thus revealed in some of the most popular concert music of all time.