Using this small application, you can easily manage Music Player while your phone is locked. Hangs on the program’s key management MP3 player. When the phone is locked and you turn it on, when clicked:

Red button: – the last track,
Menu key: – Play/Pause. 
Green button: – the next track.

Keys can be reassigned. It does not weigh in the tray there. Compatible with S^3 / Anna / Belle Smart Phones.