Opera is a form of theatre in which music has a leading role and the parts are taken by singers, but is distinct from musical theater. Such a "work" (the literal translation of Italian word "opera") is typically a collaboration between a composer and a librettist and incorporates a number of the performing arts, such as acting, scenery, costume, and sometimes dance or ballet. The performance is typically given in an opera house, accompanied by an orchestra or smaller musical ensemble, which since the early 19th century has been led by a conductor.
Opera is a key part of the Western classical music tradition. Originally understood as an entirely sung piece, in contrast to a play with songs, opera has come to include numerous genres, including some that include spoken dialogue such as musical theater, Singspiel and Opéra comique. In traditional number opera, singers employ two styles of singing: recitative, a speech-inflected style, and self-contained arias. The 19th century saw the rise of the continuous music drama.
Opera originated in Italy at the end of the 16th century (with Jacopo Peri's mostly lost Dafne, produced in Florence in 1598) and soon spread through the rest of Europe: Heinrich Schütz in Germany, Jean-Baptiste Lully in France, and Henry Purcell in England all helped to establish their national traditions in the 17th century. In the 18th century, Italian opera continued to dominate most of Europe (except France), attracting foreign composers such as George Frideric Handel. Opera seria was the most prestigious form of Italian opera, until Christoph Willibald Gluck reacted against its artificiality with his "reform" operas in the 1760s. The most renowned figure of late 18th-century opera is Wolfgang Amadeus Mozart, who began with opera seria but is most famous for his Italian comic operas, especially The Marriage of Figaro (Le nozze di Figaro), Don Giovanni, and Così fan tutte, as well as Die Entführung aus dem Serail (The Abduction from the Seraglio), and The Magic Flute (Die Zauberflöte), landmarks in the German tradition.
The first third of the 19th century saw the high point of the bel canto style, with Gioachino Rossini, Gaetano Donizetti and Vincenzo Bellini all creating works that are still performed. It also saw the advent of Grand Opera typified by the works of Auber and Meyerbeer. The mid-to-late 19th century was a golden age of opera, led and dominated by Giuseppe Verdi in Italy and Richard Wagner in Germany. The popularity of opera continued through the verismo era in Italy and contemporary French opera through to Giacomo Puccini and Richard Strauss in the early 20th century. During the 19th century, parallel operatic traditions emerged in central and eastern Europe, particularly in Russia and Bohemia. The 20th century saw many experiments with modern styles, such as atonality and serialism (Arnold Schoenberg and Alban Berg), Neoclassicism (Igor Stravinsky), and Minimalism (Philip Glass and John Adams). With the rise of recording technology, singers such as Enrico Caruso and Maria Callas became known to much wider audiences that went beyond the circle of opera fans. Since the invention of radio and television, operas were also performed on (and written for) these media. Beginning in 2006, a number of major opera houses began to present live high-definition video transmissions of their performances in cinemas all over the world. Since 2009, complete performances can be downloaded and are live streamed.
The words of an opera are known as the libretto (literally "small book"). Some composers, notably Wagner, have written their own libretti; others have worked in close collaboration with their librettists, e.g. Mozart with Lorenzo Da Ponte. Traditional opera, often referred to as "number opera", consists of two modes of singing: recitative, the plot-driving passages sung in a style designed to imitate and emphasize the inflections of speech, and aria (an "air" or formal song) in which the characters express their emotions in a more structured melodic style. Vocal duets, trios and other ensembles often occur, and choruses are used to comment on the action. In some forms of opera, such as singspiel, opéra comique, operetta, and semi-opera, the recitative is mostly replaced by spoken dialogue. Melodic or semi-melodic passages occurring in the midst of, or instead of, recitative, are also referred to as arioso. The terminology of the various kinds of operatic voices is described in detail below. During both the Baroque and Classical periods, recitative could appear in two basic forms, each of which was accompanied by a different instrumental ensemble: secco (dry) recitative, sung with a free rhythm dictated by the accent of the words, accompanied only by basso continuo, which was usually a harpsichord and a cello; or accompagnato (also known as strumentato) in which the orchestra provided accompaniment. Over the 18th century, arias were increasingly accompanied by the orchestra. By the 19th century, accompagnato had gained the upper hand, the orchestra played a much bigger role, and Wagner revolutionized opera by abolishing almost all distinction between aria and recitative in his quest for what Wagner termed "endless melody". Subsequent composers have tended to follow Wagner's example, though some, such as Stravinsky in his The Rake's Progress have bucked the trend. The changing role of the orchestra in opera is described in more detail below.