The TaifunPlayer needs a full path to access the removable SDcard, e.g .:
file:///storage/9C33-6BBD/Music/Pink Floyd - Wish You Were Here.mp3
Only an absolute path is required for access to the ASD and the other external storage, e.g.:
/storage/emulated/0/Music/loop.ogg
But the full path works as well. So use always a full path.
For more details, see also here.