prel·ude 
(prāld′, -lyd′; prĕld′, -yd′; prēld′, -lyd′)
(prāld′, -lyd′; prĕld′, -yd′; prēld′, -lyd′)n.
1. An introductory performance, event, or action preceding a more important one; a preliminary or preface.
2. Music
a. A piece or movement that serves as an introduction to another section or composition and establishes the key, such as one that precedes a fugue, opens a suite, or precedes a church service.
b. A similar but independent composition for the piano.
c. The overture to an oratorio, opera, or act of an opera.
d. A short composition of the 1400s and early 1500s written in a free style, usually for keyboard.
v. prel·ud·ed, prel·ud·ing, prel·udes
v. tr.
1. To serve as a prelude to.
2. To introduce with or as if with a prelude.
v. intr.
To serve as a prelude or introduction.
[Medieval Latin praelūdium, from Latin praelūdere, to play beforehand : prae-, pre- + lūdere, to play; see leid- in the Appendix of Indo-European roots.]
prelud′er n.
pre·ludi·al (prĭ-ldē-əl) adj.
Usage Note: How should prelude be pronounced? In our 2015 survey, 72 percent of the Usage Panel preferred a long a (pronounced “pray”) and 25 percent a short e (pronounced “prell”) for the first syllable. The absence or presence of a glide—a short (y) sound—after coronal consonants such as d, t, or l is a regional variation. People who pronounce duty as (dtē) also tend to omit the glide after the l in prelude: (prāld′). Those who pronounce duty as (dytē) will tend to include the glide: (prālyd′).