The Isengard horn comes from The Lord of the Rings, where it is tied to Saruman's fortress of Isengard and the Uruk-hai army marching to war in The Two Towers. Howard Shore's score gives Isengard a heavy, industrial brass sound, and the horn blast became shorthand for an unstoppable force on the move. Clips of the blast spread through soundboards, gaming montages and meme edits, where creators use it to announce arrivals, battles and reveals. It endures because the sound alone suggests power, menace and scale without needing any dialogue.