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, opra 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.
In England, opera's antecedent was the 17th-century jig. This was an afterpiece which came at the end of a play. It was frequently libellous and scandalous and consisted in the main of dialogue set to music arranged from popular tunes. In this respect, jigs anticipate the ballad operas of the 18th century. At the same time, the French masque was gaining a firm hold at the English Court, with even more lavish splendour and highly realistic scenery than had been seen before. Inigo Jones became the quintessential designer of these productions, and this style was to dominate the English stage for three centuries. These masques contained songs and dances. In Ben Jonson's Lovers Made Men (1617), "the whole masque was sung after the Italian manner, stilo recitativo". The approach of the English Commonwealth closed theatres and halted any developments that may have led to the establishment of English opera. However, in 1656, the dramatist Sir William Davenant produced The Siege of Rhodes. Since his theatre was not licensed to produce drama, he asked several of the leading composers (Lawes, Cooke, Locke, Coleman and Hudson) to set sections of it to music. This success was followed by The Cruelty of the Spaniards in Peru (1658) and The History of Sir Francis Drake (1659). These pieces were encouraged by Oliver Cromwell because they were critical of Spain. With the English Restoration, foreign (especially French) musicians were welcomed back. In 1673, Thomas Shadwell's Psyche, patterned on the 1671 'comdie-ballet' of the same name produced by Molire and Jean-Baptiste Lully. William Davenant produced The Tempest in the same year, which was the first musical adaption of a Shakespeare play (composed by Locke and Johnson). About 1683, John Blow composed Venus and Adonis, often thought of as the first true English-language opera.
Blow's immediate successor was the better known Henry Purcell. Despite the success of his masterwork Dido and Aeneas (1689), in which the action is furthered by the use of Italian-style recitative, much of Purcell's best work was not involved in the composing of typical opera, but instead he usually worked within the constraints of the semi-opera format, where isolated scenes and masques are contained within the structure of a spoken play, such as Shakespeare in Purcell's The Fairy-Queen (1692) and Beaumont and Fletcher in The Prophetess (1690) and Bonduca (1696). The main characters of the play tend not to be involved in the musical scenes, which means that Purcell was rarely able to develop his characters through song. Despite these hindrances, his aim (and that of his collaborator John Dryden) was to establish serious opera in England, but these hopes ended with Purcell's early death at the age of 36.
Following Purcell, the popularity of opera in England dwindled for several decades. A revived interest in opera occurred in the 1730s which is largely attributed to Thomas Arne, both for his own compositions and for alerting Handel to the commercial possibilities of large-scale works in English. Arne was the first English composer to experiment with Italian-style all-sung comic opera, with his greatest success being Thomas and Sally in 1760. His opera Artaxerxes (1762) was the first attempt to set a full-blown opera seria in English and was a huge success, holding the stage until the 1830s. Although Arne imitated many elements of Italian opera, he was perhaps the only English composer at that time who was able to move beyond the Italian influences and create his own unique and distinctly English voice. His modernized ballad opera, Love in a Village (1762), began a vogue for pastiche opera that lasted well into the 19th century. Charles Burney wrote that Arne introduced "a light, airy, original, and pleasing melody, wholly different from that of Purcell or Handel, whom all English composers had either pillaged or imitated".
Besides Arne, the other dominating force in English opera at this time was George Frideric Handel, whose opera serias filled the London operatic stages for decades, and influenced most home-grown composers, like John Frederick Lampe, who wrote using Italian models. This situation continued throughout the 18th and 19th centuries, including in the work of Michael William Balfe, and the operas of the great Italian composers, as well as those of Mozart, Beethoven and Meyerbeer, continued to dominate the musical stage in England.
The only exceptions were ballad operas, such as John Gay's The Beggar's Opera (1728), musical burlesques, European operettas, and late Victorian era light operas, notably the Savoy Operas of W. S. Gilbert and Arthur Sullivan, all of which types of musical entertainments frequently spoofed operatic conventions. Sullivan wrote only one grand opera, Ivanhoe (following the efforts of a number of young English composers beginning about 1876), but he claimed that even his light operas constituted part of a school of "English" opera, intended to supplant the French operettas (usually performed in bad translations) that had dominated the London stage from the mid-19th century into the 1870s. London's Daily Telegraph agreed, describing The Yeomen of the Guard as "a genuine English opera, forerunner of many others, let us hope, and possibly significant of an advance towards a national lyric stage."
In the 20th century, English opera began to assert more independence, with works of Ralph Vaughan Williams and in particular Benjamin Britten, who in a series of works that remain in standard repertory today, revealed an excellent flair for the dramatic and superb musicality. More recently Sir Harrison Birtwistle has emerged as one of Britain's most significant contemporary composers from his first opera Punch and Judy to his most recent critical success in The Minotaur. In the first decade of the 21st century, the librettist of an early Birtwistle opera, Michael Nyman, has been focusing on composing operas, including Facing Goya, Man and Boy: Dada, and Love Counts. Today composers such as Thomas Ads continue to export English opera abroad.
Also in the 20th century, American composers like Leonard Bernstein, George Gershwin, Gian Carlo Menotti, Douglas Moore, and Carlisle Floyd began to contribute English-language operas infused with touches of popular musical styles. They were followed by composers such as Philip Glass, Mark Adamo, John Corigliano, Robert Moran, John Coolidge Adams, Andr Previn and Jake Heggie.