Volume 3: 1771 Edition of the Encyclopedia Britannica!
Overture
Overture, or Ouverture, opening or preluding; a term used for the solemnities at the beginning of a public act or ceremony; an opera, tragedy, concert of musick, etc.
The overture of the theatre, or scene, is a piece of musick usually ending with a fugue: the overture of a jubilee is a general procession, etc.