prelude

noun

• 1an action or event serving as an introduction to something more important:a ceasefire had been agreed as a prelude to full peace negotiations

• 2an introductory piece of music, most commonly an orchestral opening to an act of an opera, the first movement of a suite, or a piece preceding a fugue.
• a short piece of music of a style similar to a prelude, especially for the piano.
• the introductory part of a poem or other literary work.

verb

• serve as a prelude or introduction to:the bombardment preluded an all-out final attack