Requiem for a Tower
From Tolkien Gateway
Requiem for a Tower is the name for the up-beat song present in a trailer for Peter Jackson's The Two Towers. The song is one of the most memorable tracks from Peter Jackson's films but unfortunately was not even originally created for the movies. Instead, it was the main theme for the 2000 movie Requiem for a Dream. It was called Lux Aeterna, composed by Clint Mansell.
For the trailer the song was re-orchestrated by The Ant Farm with three composters (Simone Benyacar, Dan Nielsen and Veigar Mairgersson), forty musicians and twenty choral voices.
The song would later be reused in The Hunt for Gollum, accompanying a fight sequence of Aragorn.