What he said.
I think Apple have done a great job with this - Music appears to use very little resources.
I had it streaming to a Bluetooth speaker from my iPhone 6 for a few hours yesterday. The battery dropped a little but it was like 10% - great.
Compare Music to the resource hog that's iHeart Radio - no comparison.
I should add that was using Beats 1.
Also I really like the implementation of the global dj concept.
The Alligator Hour +1 and Julie from London +1