This a very basic AddOn that adds any desired sound to LibSharedMedia for use in LSM-compatible AddOns.
It has no in-game configuration and new sounds must be added to the core.lua file in the format provided. Lua files can be opened and changed in any text editor (e.g. Notepad, Notepad++, TextEdit). Sounds can be added from anywhere inside the WoW folder, including default game sounds and sounds from other AddOns.
By default, this only adds one sound to LSM: "Vengeance burns!", spoken by Kael'thas in Magister's Terrace.
Thanks to Astran @ Blackwater Raiders US for the idea and to Elkano for creating LSM.