Continue Playing Sound on Android while Locked

Hello, I think this one should be pretty simple, but you never know. Tried searching but I might be using the wrong terms.

Anyway, how do I allow my app to continue playing sound/music while the phone is locked (black screen)?

I am not talking about minimizing the app. The app will still be active, but the phone will be locked. I know many apps allow this (Spotify, Audible, etc) so it isn't a design limitation of android. I am just curious how this is done through unity.