Overture (noun)

1. A piece of music typically played at the beginning of an opera or ballet.
2. A preliminary proposal or offer made in negotiations or discussions.
3. An approach or opening to a subject, opportunity, or relationship.
4. An introduction or prelude to a larger work or event.

Origin:

Mid 17th century: from french ouverture, from ouvrir 'to open', from latin aperire.

Examples:

1. The overture to the opera was a beautiful and uplifting piece of music.
2. The company made an overture to the union to start negotiations.
3. The ambassador's speech was an overture to improved relations between the two countries.
4. The book was an overture to a series of novels.
5. The movie's overture set the mood for the rest of the film.