overture, instrumental musical composition written as an introduction to an opera, ballet, oratorio, musical, or play. The earliest Italian opera overtures were simply pieces of orchestral music and were called sinfonie. Jean Baptiste Lully standardized the French overture, using an opening section in pompous chordal style and dotted rhythms followed by a fugal section. This type of overture was much imitated, an example being the overture to Handel's Messiah. In some of the 17th-century Neapolitan operas, to some extent in Jean Philippe Rameau's operas and most notably in Gluck's, the overture began to foreshadow what was to come in the work's tunes. In many 19th-century operas and 20th-century musicals the overture is simply a potpourri of the work's tunes. The concert overture, a composition in one movement that may be in any of a variety of styles, arose in the 19th cent.; the overtures of Brahms, Mendelssohn, and Beethoven are outstanding.

Musical introduction to a larger, often dramatic, work. Originating with Claudio Monteverdi's Orfeo (1607), overtures served as openings for operas. The large-scale two- or three-part “French overture” invented by Jean-Baptiste Lully (1658) for his operas and ballets was widely imitated for a century. The sinfonia, the standard Italian overture form in the late 17th and 18th centuries, was a principal precursor of the three-part sonata form and thus provided the model for the earliest symphonies, which consisted of three movements. In the 19th century, overtures independent of any larger work usually illustrated a literary or historical theme (see symphonic poem). Overtures to operettas and musicals have traditionally been medleys of their themes.

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