Introduction to an opera or other large musical work.

An extended orchestral introduction to an opera, ballet, or similar type of musical presentation.

An introductory movement to an opera or substantial work. In opera, the overture usually contains examples of the major musical themes that will appear throughout the work - a type of trailer for what is to come.

The seventeenth century opera overture, also known as sinfonia. The sinfonia was established as an introduction to the opera by A. Scarlatti. It has differences in Italian and French style. The French overture has two sections: slow-solemn chordal introduction with dotted rhythm in simple duple/quadruple time followed by a fast contrapuntal (fugal allegro) section. Rameau's overtures introduce a theme to reappear in the opera later on. The Italian overture has the fast-slow-fast structure. The overture was the forerunner of the symphony. Later an extra movement in triple time was added between the slow and the last movements (minuet - scherzo). The Italian type sinfonia provided the basis of the future orchestral symphony.