Music consists of repetition (similarity) and contrast. The unity in this framework is achieved through a refrain section or basso ostinato as binding agents, recurrent use of the same melodic or rhythmic motif (persistent figuration, idee fixe, leitmotif as means of creating thematic unity), tonal plan (starting and finishing in the same key visiting related keys in between), use of a certain recurrent interval in all significant melodic material (intervallic relationship), or thematic transformation (developing related themes from an original theme in different parts of the piece). In Baroque music, a single melodic or rhythmic figure representing a single mood or affekt establishes the unity.