Origin of Magic?

How did magic start in your world? In my world it started when a god from a different universe died and exploded so violently the sound and energy of the explosion is still around today. Magic users can "hear the rhythm" and harness the energy through their bodies, Magic users are called instruments. Depending on the race they use these instruments in different ways.

Orcs use instruments or Spiri caste to get visions of the future, past, and to predict the next signs of their gods. Dwarves use their instruments to make magical artifacts, weapons, and armor. Why have a few people use magic when you can make 1000 magic weapons.