When the Bloodlust buff is applied to the player, plays a sound file of Sylvanas' "For the Horde!" yell

By default this activates on any haste increase of 25-30% (bloodlust, time warp, heroism - yea, even that, ancient hysteria and drums). If you'd like to turn it off on some, check the options in Interface -> AddOns -> For The Horde

This started as a request from the WoW forums: https://us.battle.net/forums/en/wow/topic/20759371239?page=1

If you really want something like this, but it's not working from you, WeakAuras will probably be able to do the same thing if you know how to use that. You can likely just set it to trigger off the auras you want to use and that is a highly tested addon.