A transition is a passage of music composed to link one section of music to another. Transitions often function as a moment of transformation and may, or may not in themselves, introduce new, musical material. For example, transition may be defined as different from a subordinate theme (rondo form) or a developmental core. In sonata form, a retransition (the transition to the recapitulation) is the last part of the development section which prepares for the return of the first subject group in the tonic, most often through a grand prolongation of the dominant seventh.