Don Carlos was written for performance in Paris. This has made a problem for the reputation of the opera, because it was tradition in France to write very long operas. They always included a lot of ballet music as well as the singing. Verdi’s opera was in five acts, and when it was performed in other countries it was too long for people’s tastes, so many cuts were made, including, at first, the whole of Act I. This is a great pity, because a lot of the music in Act One is very important, with tunes which also come later in the opera. Since the beginning of the 20th century most of the music of Act I is usually performed. There have been many different versions performed, with different parts of the opera cut. When the opera is sung in Italian it is called "Don Carlo".