section_path: Operatic terminology
section_name: Operatic terminology
paragraph_text: Operatic terminology
  
  The words of an opera are known as the libretto (meaning "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.