The characteristic of Wagner’s music is that the orchestra is its main tool of expression. A symphony consists of a leading motive that is repeated many times. These motives describe the characters, natural phenomena, characters' emotions and events in the play. Many short leading motives alternate, deform, and combine at the same time, developing in the form of a continuous symphony, constituting Wagner's "endless melody" feature. The structural requirements of an opera are: there is the unity of a symphony movement, which is consistently implemented throughout the play and consists of many basic themes scattered throughout the play. These themes contrast with each other, complement each other, change each other, and interweave with each other. The rules for separation and combination of themes are determined according to the needs of plot development.