prelude

Short definition from Wiktionary

Noun

1. 1
   An introductory or preliminary performance or event.
2. 2
   A short, free-form piece of music, originally one serving as an introduction to a longer and more complex piece; later, starting with the Romantic period, generally a stand-alone piece.
3. 3
   A standard module or library of subroutines and functions to be imported, generally by default, into a program.
4. 4
   A forerunner to anything.

Verb

1. 1
   To introduce something, as a prelude.
2. 2
   To play an introduction or prelude; to give a prefatory performance.