UNTESTED: 
Added -f# option to pass on the frequency to play the file at (with formats that support it such as MUS (doom) format. 
Extern’d _cvt_reset_options and _cvt_get_options. _cvt_reset_options may be able to go back to static def. 
Added error for MUS (doom) files. 
Optimised MUS (doom) header check in wildmidi-devtest. 
Added _WM_ParseNewMus().
Added FIXME:’s for areas that I need to check and work on.