Adding subwoofer to Full-Ragne Speakers question

Especially for music...
The sub will surely add deeper base in the bottom end side..., I guess that's the purppose of adding a sub to begin with...

However, does it help in the midrage area?
Taking some load off of those woofers on the speakers so that they can concentrate on the midrage? or it doesn't matter as far as midrage's concerned.

I think I never got clear answer to this question, yet...