The difference between musicals and operas is that musicals often use different types of pop music and popular music instrument arrangements; dialogue without musical accompaniment is allowed in musicals; and it is not used in musicals. Some traditions of opera, for example, there is no distinction between recitative and aria, and the singing method is not necessarily bel canto. However, the dividing line between musicals and operas is still controversial among many scholars. For example, Porgy and Bess (Taiwan translation "Beggars and Sluts") composed by Gershwin was also called "Porgy and Bess". Opera, folk opera (Folk Opera) and musicals. Some musicals such as Les Misérables have musical accompaniment from beginning to end, while some operettas such as Carmen have dialogue. Musicals generally have more dance elements than operas, and early musicals were even song and dance performances without scripts. Although the famous opera composer Richard Wagner had already proposed Gesamtkunstwerk (Gesamtkunstwerk) in the mid-19th century, he believed that music and drama should be integrated into one. But in Wagner's musical dramas, music is still the dominant factor. In contrast, the drama and dance elements in musicals are more important.