Keep Android App running when screen is locked

I've done a large google search on this issue yet i can't seem to find an answer to this question.

I have my app able to run without the screen turning off by setting the Screen to never sleep which works fine as it ran all night long.

Problem is, it's not very power saving and was wondering if there is a way you can keep a unity app running when the power button has been pressed that then turns the screen off and puts it into lock mode, at the moment the app is i'm assuming "suspended" and carries on when the screen is unlocked at the moment it was locked.

It would be handy for this to happen for the audio element of the app.

Many thanks