pone
2
Action: Format Value
Field: _FILENAME
Formatstring: $regexp(%_filename%,(.) (featuring|Featuring|FEATURING|ft|Ft|FT|feat|Feat|FEAT)(. | )(.) - (.*),$1 - $5 $2$3$4)
If you want to change the feat inside you tag fields, look here:
/t/11096/1
or here (German):
/t/11291/1