I use below code to play audio in background:
String[] Path = new String[] {path1, path2, ...}; mMediaPlayer.setDataSource(Path[i]); mMediaPlayer.prepare();
You need to set an OnCompletionListener to your MediaPlayer, in the listener set the source to path2, prepare and play. http://developer.android.com/reference/android/media/MediaPlayer.OnCompletionListener.html