Nouns

(n)preliminary, overture, preludesomething that serves as a preceding event or introduces what follows“training is a necessary preliminary to employment”, “drinks were the overture to dinner”
(n)preludemusic that precedes a fugue or introduces an act in an opera

Verbs

(v)preludeserve as a prelude or opening to
(v)preludeplay as a prelude