Most musicals produced for the stage combine songs and dialogue to convey the arc of a story. When a particular song is repeated later in the show, it is called a reprise. This may be a shorter version of the original song, or it may be altered for ensemble singing. Many composers of musicals use this technique to connect an earlier scene with the finale or curtain call.
One common use of a reprise gives the song a different context in the storyline. In the musical Annie, for example, the title character first performs the song "Tomorrow" as a solo. In the context of the scene, she is trying to remain optimistic during a very difficult moment. During the triumphant final scene, Annie and her adopted family sing "Tomorrow" again, which serves this time as a positive anthem for the future. The reprise helps the audience reconnect with the earlier solo performance.
Another function of a reprise is to bring more energy to a scene. Some musicals can have three or more acts, which often means a running time of two hours or more. Audiences may respond well to a particular song in the first act, so the composers may use a version of it in the final act to rebuild audience interest. Other characters may sing the song as comic relief, for example. In the musical Oliver, one sympathetic character performs a brief reprise of her song "As Long as He Needs Me" as a reminder of her dedication to the title character.
Some musicals use the reprise as a recurring thematic piece. In the musical South Pacific, snippets of the romantic song "Some Enchanted Evening" are reprised several times as the lead romantic couple are reunited or separated by their wartime duties. When the final version is performed, the song has taken on a much deeper significance for the characters. A reprise is often re-orchestrated to provide a stronger ending than the original version. This dramatic form is often heard during the end credits of filmed musicals.