What is "concert overture"

Overture \O"ver*ture\, [OF. overture, F. ouverture, fr. OF. ovrir, F. ouvrir. See Overt.]

1. An opening or aperture; a recess; a chamber. [Obs.]
   --Spenser. ``The cave's inmost overture.''
   --Chapman.

2. Disclosure; discovery; revelation. [Obs.]

   It was he That made the overture of thy treasons to us.
   --Shak.

3. A proposal; an offer; a proposition formally submitted for consideration, acceptance, or rejection. ``The great overture of the gospel.''
   --Barrow.

4. (Mus.) A composition, for a full orchestra, designed as an introduction to an oratorio, opera, or ballet, or as an independent piece; -- called in the latter case a concert overture.