prelude

Definitions:

To serve as an introduction.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (verb, noun) (v. & n.) (verb, noun)
Introductory piece of music; something that precedes.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)
To introduce; to play before.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (verb) (v.) (verb)
To serve as an introduction to; precede.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (verb) (v. t.) (verb transitive)
To play before: to precede, as an introduction.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (verb) (v. t.) (verb transitive)
To precede; to introduce a piece of music with a voluntary movement; to serve as an introduction to.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (verb) (v.) (verb)
To perform a prelude; preface.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (verb) (v. i.) (verb intransitive)
Prelusive.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)
A short piece of music played as an introduction to a longer piece; preface; something done to prepare the way for something more important.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
A short piece of music before a longer piece: a preface: a forerunner.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
Something introductory or preparatory, as indicative of what is to follow: a forerunner; a short strain of music before a regular piece or concert.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
A short musical flourish or voluntary played before the commencement of the piece to be performed; the overture; something introductory; something which indicates a future event.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)

Usage examples:

Jennie was playing a soft prelude as a gentle warning to a few of those who seem ever to find silence a physical difficulty.
- In the Wilderness by Robert Hichens
One of the youngest pupils stood, violin in hand, while, at the piano, Betty Chase was playing the prelude
- Dorothy Dainty at Glenmore by Amy Brooks
Presumably, if I accept your apologies now, it will be a prelude to further visits by impudent police officers.
- A Mysterious Disappearance by Gordon Holmes