Overture

Overture (from French ouverture, lit. "opening") in music is the term originally applied to the instrumental introduction to an opera. During the early Romantic era, composers such as Beethoven and Mendelssohn began to use the term to refer to independent, self-existing instrumental, programmatic works that presaged genres such as the symphonic poem. These were "at first undoubtedly intended to be played at the head of a programme".

The idea of an instrumental opening to opera existed during the 17th century. Peri's Euridice opens with a brief instrumental ritornello, and Monteverdi's L'Orfeo (1607) opens with a , in this case a fanfare for muted trumpets. More important, however, was the prologue, which comprised sung dialogue between allegorical characters which introduced the overarching themes of the stories depicted.

As a musical form, however, the French overture first appears in the court ballet and operatic overtures of Jean-Baptiste Lully, which he elaborated from a similar, two-section form called Ouverture, found in the French ballets de cour as early as 1640. This French overture consists of a slow introduction in a marked "dotted rhythm" (i.e., exaggerated iambic, if the first chord is disregarded), followed by a lively movement in fugato style. The overture was frequently followed by a series of dance tunes before the curtain rose, and would often return following the Prologue to introduce the action proper. This ouverture style was also used in English opera, most notably in Henry Purcell's Dido and Æneas. Its distinctive rhythmic profile and function thus led to the French overture style as found in the works of late Baroque composers such as Johann Sebastian Bach. The style is most often used in preludes to suites, and can be found in non-staged vocal works such as cantatas, for example in the opening chorus of Bach's cantata Nun komm, der Heiden Heiland, BWV 61. Handel also uses the French overture form in some of his Italian operas such as Giulio Cesare.

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