Nineteenth-century Russian operas almost invariably abound in set dance numbers. Eugen Onegin, composed in 1877, the year of Tschaikowsky's marriage, is no exception. Several of its dances, though, are not merely colourful diversions but form an integral part of the action. In the swaggering Polonaise which opens the third act, the milieu of the fashionable St.Petersburg society, which forms the background to the opera's final scenes, is introduced.