An opera is a dramatic work which blends elements of theater, dance and music. Almost all of the dialogue is sung, or at least delivered in a pitched tone. Opera composers generally start with a written script of the storyline called a libretto, or "little book." The libretto may be a completely original story, or an adaptation of an existing literary piece. The words and storyline form the basic structure of an opera.
The composer then decides which lyrics lend themselves to a full musical treatment and which just move the story forward thematically. If the lyrics reveal the true emotions of a character, such as love or fear, the opera's composer may create a fully scored song called an aria. An aria might be sung by any of the main characters, but quite often it works as a showcase for a particularly strong singer. Many arias have become quite familiar worldwide.
An opera also contains numerous moments when the characters are essentially having conversations amongst themselves. For those scenes, the opera's composer may use a musical form called a recitative. A recitative is a piece of dialogue set to music, although the music may not be very interesting to the audience. The performer of a recitative may sing his or her lines without much concern for an actual melody. Some modern composers no longer use recitatives, but allow the actors to speak their lines normally. In the classic form, however, all dialogue is set to some sort of music.
Many musical historians suggest the first opera to be performed was a piece called Dafne, written by Jacopo Peri in 1598. It was not considered a commercial success in its day, and is rarely performed by modern opera companies. The first composer whose work still enjoys popularity in the opera world was an Italian musician named Claudio Monteverdi. Monteverdi is credited with helping music theory transition from the Renaissance style to the Baroque style exemplified by composers such as J.S. Bach.
Opera has survived as a musical form primarily because it can adapt, or at least be adapted, to whatever form of music is popular at the time. Over the years, it has incorporated folk music, patriotic or nationalistic anthems, jazz, blues and even rock music. The staging of an opera can also be quite creative and breathtaking in scale. Performing the entire Rings of the Nibelung cycle by Richard Wagner, for example, can take several weeks of scheduled productions.