Groove music not playing when locked

[minimullet]

Quick story is I downloaded/ converted some youtube videos in to mp3 format on my laptop, and then put them on my phone (950 if that helps) and they play perfectly but when I lock the screen it stops playing. Is there some way I can fix this?

 

[640xxxl]

Currently, no. It's OS issue and happens with every single player. Every app let run in background when phone goes standby is "killed".