WoW API is like a list of functions/methods that Blizzard gives to players in order to make addOns.
For example:
- CastSpellByName is a function that allows player to cast a spell by giving the name of it.
- UnitName is a function that returns the name of an unit (i.e. target, player, focus, etc).
Here is the list:
http://wowprogramming.com/docs/api, please note that it is updated to WoD, so not all functions are available in Vanilla and some might got removed. That's why a lot of addOns stop working after a release of an expansion.
I looked for most
common music player addOns, EpicMusicPlayer and Soundtracker, and both were created when TBC was released.
Try both, maybe it's working for Vanilla expansion.
I also made one for Cataclysm,
BlindedByFear. It should work partially for Vanilla (listening your music - dunno if
PlayMusic was available in Vanilla, if not, switch to
PlaySoundFile), but the share-part should be broken (easy to fix for Vanilla I guess).