Song of Courage

Whenever the hero or his allies are under great odds, even seeming doomed to be destroyed by a single foe, army, or unstoppable force of nature, there's the chance that one of the main characters will give a speech or word that'll conjure the power of either an unseen choir, instrumental band or actually a character in the scene that'll rally their spirits to face their death and carry on with dignity and valor.

The heroes don't necessarily have to succeed- strictly speaking they don't even have to live past the endeavor, but the Song of Courage at least makes them look cool as they fall. The Song isn't about not going gentle into that good night- it's about triumph against the fear of death, and the people singing it may simply be awaiting their imminent deaths, knowing that trying to fight it won't help.

The Song of Courage can either be heard by the characters, or it could just be ambience for the sake of the audience.

Sister trope of The Song Before the Storm.

Anime & Manga

 * Seto no Hanayome has a literal Song of Courage, that Sun can use as Nagasumi's Theme Music Power-Up. Lunar has a similar ability called the "Song of War", but the effects are... somewhat less refined.

Film

 * "Do You Hear the People Sing?" from Les Misérables.
 * "Into the Fire" from The Scarlet Pimpernel.
 * "A Spark Inside Us" gets used throughout The Princess and the Goblin to both repel goblins and embolden the heroes.

Live Action TV

 * "Walk Through the Fire" from Buffy the Vampire Slayer's Musical Episode, "Once More, With Feeling".
 * "Yo-A-O" from Lexx, also known as "The Fight Song of the Brunnen-G". The lyrics are in in the (fictional) language of the (fictional) Brunnen-G, but a translation exists and it basically amounts to a call to battle, a declaration of what is worth fighting for (one's home and heart), and a vow to win or die but always as a Warrior Poet. Traditionally sung before (or during) a hopeless battle or Heroic Sacrifice.
 * Considered by many fans to be Crowning Music of Awesome it can be found (with lyrics and translation) here: http://www.youtube.com/watch?v=qMp3ogAJGUc

Music

 * "Light Up the Night" by The Protomen.

Video Games

 * Theme to Fire Emblem.
 * Several songs from Final Fantasy 9, such as Those Whom I Must Protect and You Are Not Alone.
 * GONG from Super Robot Wars Alpha 3. The song that gives our heroes the courage to stand up against the LITERAL God of Death and is sung by EVERY SINGLE MECHA PILOT FROM EVERY SINGLE SIGNIFICANT MECHA SERIES IN THE HISTORY OF ANIME. Yeah, it is that badass
 * The in Metal Gear Solid 4: Guns of the Patriots can be seen in here, Tear Jerker included.

Western Animation
"AQUAMAN: (to Captain Atom) You don't look roused."
 * In The Simpsons episode "Bart's Comet", Ned Flanders faces his apparent death at the comet by singing "Que Sera Sera", which unsettles the Springfield residents who kicked him out of his own shelter. When they all decide to leave and face the comet together, they join Flanders in the song creating an impressive chorus.
 * Played with in Batman the Brave And The Bold with AQUAMAN'S Rousing Song of Heroism.