A leitmotif is a short, recurring musical phrase, or sometimes a chord progression or rhythm, in an opera, tone poem, or movie that is associated with a particular person, place, event or idea. Leitmotifs are used to reinforce dramatic action, to provide psychological insight into the characters, and to recall or suggest ideas relevant to some event, and they can play an important role in providing cohesion to lengthy works. They are often modified in terms of rhythm, harmony and/or orchestration, or even combined with other leitmotifs, as a work progresses.