Epigraph

An epigraph is a literary technique where a line excerpted from another work is quoted before the beginning of the work itself. Ordinarily the work quoted exists in the real world, but in some cases it is itself fictional.

In fan fiction, songs are used with some regularity.

Official works

 * :  by (real-world), and Taer'thaiemenh by V. Raiuhes Athaefvthe (fictional)
 * :  by and Lays of Ancient Rome by Thomas Babington Macaulay (real-world), and Contemplations by tr'Hmaellieh (fictional) 

Fan fiction

 * Reality is Fluid: "" by
 * "Saith Daepahr hrrafv Llaiirevha, Part II": by
 * "The Silence Ends": "Welcome to the Universe" by 30 Seconds to Mars, and by
 * "Solaere ssiun Hnaifv'daenn": The Qur'an 17:53-54 ( translation)
 * Beat the Drums of War: Chapter 2 uses "Steam-powered Samurai" by Escape the Clouds.