Look Android is using AudioPlaybackPreview or someother named activity, to handle the song playback from fileManager or any other place .
Actually you want to use the default Playing activity ,which is used to show all the controls and all .Dear it's not possible to use that Activity , since it had been linked to someother service having data of all the songs and all paths. This playing Activity has control of next atnd previous and all , that is linked with one playback service.
Third thing is that , as far as i know that S3 is almost providing the same layout for playing the song from filemanager or for plaaying from any other activity. But the problem with that is that when u go back from there , it will stop the playing song.
Refer to android music player source code , u will understand why it's not possible to launch that activity.