A performance that's repeated or added to the regular performance is called an encore. If you're deaf from last night's concert, it might be because the band played for two hours and then did a thirty minute encore.
Encore is a French word meaning again. Audiences often yell, "Encore!" if a play, song, or other act has been particularly good. In essence they are shouting, "Again!" After a musical number, the encore may take the form of a repeated verse or chorus. At the end of a concert, the encore may be a whole extra set. The word is sometimes used sarcastically: "Well, you flunked math. What are you going to do for an encore?"