"C" series apps by developer "Astoncheah" are built specifically for C-onvenience and C-ustimization. There have been many of these apps, but the most recent app in the series aims to give you full control of your Device's volume rocker while the screen is turned OFF. Talk about convenience. My initial instinct is to pick up my phone and hit the volume rocker to turn up the volume or turn the volume down even when the screen is turned off, but more times then not i find myself turning the screen on so that I can then adjust my volume. The C volume rocker app allows you to control your volume rocker regardless of whether or not the screen is on as long as Media is playing. Grab this app from the source link below.