An opera is normally divided into two, three, four or even five acts. In older operas the music was mostly recitative and arias. During the recitative things would happen in the story. The aria was a song for a solo singer, a setting of a lyric. As well as recitative and aria there would be choruses. The chorus were a group of singers who sing in the crowd scenes. The opera would start with an overture for the orchestra. The overture would usually include tunes that are going to be heard later in the opera. 