Actually, you can find out the solution using the trick from post #2 in this thread.
To avoid side effects .... set ...
Filter: TITLE MATCHES "[[({<]?\s*(?:featuring|feat\.?|ft\.?).+?[])}>]?" AND NOT ARTIST MATCHES "[[({<]?\s*(?:featuring|feat\.?|ft\.?).+?[])}>]?"
The following proposal removes the sequence "featuring somebody" from TITLE and appends it to ARTIST, that means, the "featuring somebody" supplement will be swapped or exchanged from TITLE to ARTIST.
Additionally, different spellings and abbreviations of "featuring" will be replaced by the abbreviation "feat.".
Action: Guess values
Source format:
%ARTIST%$regexp(%TITLE%,'^(.+?)\s+[[({<]?\s*(?:featuring|feat\.?|ft\.?)\s*([^])}>]+)\>\s*[])}>]?(.*)$',' feat. $2$3+++$1',1)
... or ...
%ARTIST%$regexp(%TITLE%,'^(.+?)\s+[[({<]?\s*(?:featuring|feat\.?|ft\.?)\s*([^])}>]+)[])}>]?(.*)$',' feat. $2$3+++$1',1)
Guessing pattern:
%ARTIST%+++%TITLE%
From:
ARTIST=Bob Fuller
TITLE= ...
Las Vegas ft Annie Spider
Las Vegas ft. Annie Spider
Las Vegas feat Annie Spider
Las Vegas feat. Annie Spider
Las Vegas featuring Annie Spider
Las Vegas [ft Annie Spider]
Las Vegas (ft Annie Spider)
Las Vegas {ft Annie Spider}
Las Vegas
Las Vegas [ feat. Annie Spider ]
Las Vegas ( feat. Annie Spider )
Las Vegas { feat. Annie Spider }
Las Vegas < feat. Annie Spider >
Las Vegas [ feat. Annie Spider ] [INSTRUMENTAL]
To:
TITLE=Las Vegas
ARTIST=Bob Fuller feat. Annie Spider
... resp. in the last case ...
ARTIST=Bob Fuller feat. Annie Spider [INSTRUMENTAL]
The following proposal removes the sequence "featuring somebody" from ARTIST and appends it to TITLE, that means, the "featuring somebody" supplement will be swapped or exchanged from ARTIST to TITLE.
Additionally, different spellings and abbreviations of "featuring" will be replaced by the abbreviation "feat.".
To avoid side effects .... set ...
Filter: ARTIST MATCHES "[[({<]?\s*(?:featuring|feat\.?|ft\.?).+?[])}>]?" AND NOT TITLE MATCHES "[[({<]?\s*(?:featuring|feat\.?|ft\.?).+?[])}>]?"
Action: Guess values
Source format:
%TITLE%$regexp(%ARTIST%,'^(.+?)\s+[[({<]?\s*(?:featuring|feat\.?|ft\.?)\s*([^])}>]+)[])}>]?(.*)$',' feat. $2$3+++$1',1)
Guessing pattern:
%TITLE%+++%ARTIST%
The following proposal sets the abbreviation "feat. somebody" into round brackets in the target field, giving "(feat. somebody)".
Action: Guess values
Source format:
%TITLE%$regexp(%ARTIST%,'^(.+?)\s+[[({<]?\s*(?:featuring|feat\.?|ft\.?)\s*([^])}>]+)[])}>]?(.*)$',' (feat. $2$3)+++$1',1)
Guessing pattern:
%TITLE%+++%ARTIST%
DD.20120708.2030.CEST
Edit.DD.20120728.1616.CEST
Edit.DD.20131029.0900.CET