An oratorio is an extended composition for vocal soloists, chorus and orchestra; the narrative text is usually based on scripture or biblical stories but is non-liturgical. Although the oratorio is often about sacred subjects, it may also deal with semi-sacred subjects. This large-scale work is often compared to an opera, but unlike the opera, the oratorio often doesn't have acting, costumes and scenery. The chorus is an important element of an oratorio and the narrator's recitatives help move the story forward.