Mysterious plugin guy: vio2sf doesn't support _lib tags according to PSF specification:
"I tried similar _lib / _lib2, and it does not seem to be implemented properly, according to the standards.
Proper procedure of _lib loading.
_lib = Main rom with everything required. mini2sf = patch rom that changes the song. Usually one or two bytes patched. _lib2, _lib3, etc.. = patch rom that changes other bytes, or loads in other data in place of existing data.
So basically, _lib is loaded first right into ram. _lib2 is then patched into the memory that _lib takes up. If this would exceed boundaries that _lib took, reallocate the size of _lib.
Then mini2sf is applied on top of _lib, same procedures.
This really should have been implementted into the player even if it wasn't used at the moment. If you need some help, look at the source code of highly advanced. It is implemented there."
Also, vio2sf 0.18 has a severe bug in _lib loading, which makes every set unplayable:
"There's a bug in the xsflib loading code, the default behaviour loads mini2sf first and then overlays the 2sflib on to that.
Since mini2sf have the song select code, and the driver 2sflib has only a constant value for that, what you will get is song 0x00 playing for *all* files.
Adding _vio2sf_loader_type=1 tag to all mini2sf files will fix the situation, but isn't obviously the intended solution."