There are also many human musicians in the Bible, are all humans musicians?
Various scriptures make a point to claim most Angels exist to praise and worship God and several times it mentions "and the Angels sing..."
Although the Cherubim are known as the music leaders of Heaven.
I'm pretty sure all of Angels, Humans, and all of Creation exists to praise and worship God. I don't know of anything that would specifically support all angels being innately deserving of the musician identifier and not humans.
At this point it doesn't matter for the game, (as they already said that Musicians are limited to humans), but several times it is mentioned of All Angels or great multitudes of angels singing. That and again, the Cherubim are directly stated as the ones who lead the worshipping of God and specifically songs sung to worship God.
