hi i have this problem i can't solve .
ARTIST: Samson Francois
TITLE: Johann Sebastian Bach - toccata adagio.... and so on..
I want:
ARTIST: Johann Sebastian Bach-Samson Francois
TITLE: toccata adagio.... and so on..
that's to say that i have to know where the " - " is and everything before the " - " must be placed before the actual artist.
Thank u.... 
Action: Guess Values
Source Format: $regexp(%title%,(.+?) - (.+),$1)-%artist% - $regexp(%title%,(.+?) - (.+),$2)
Guessing Pattern: %artist% - %title%
Actiontype 7: Import tag fields (guess values)
Source format: $regexp(%ARTIST%'==='%TITLE%,'^(.+?)===(.+?)÷-÷(.+?)$','$2-$1===$3')
Guessing pattern: %ARTIST%===%TITLE%
Note: Replace each special ÷ character with one space character.
From:
ARTIST: Samson Francois
TITLE: Johann Sebastian Bach - toccata adagio
To:
ARTIST: Johann Sebastian Bach-Samson Francois
TITLE: toccata adagio
I want to mention that the proposal from user 'pone' in post #2 has the advantage of not using a surrogate delimiter string.
DD.20110312.1724.CET
Thank U.... works like a charm... 
Hey guys-
I had a similar question, but one I don't know how to make it work given that it requires making a second artist tag.
Detlev, on a previous post, I had asked how to move stuff in [ ] from the TITLE to the ARTIST, and you had suggested the following:
Action #1
Actiontype 5: Format value
Field: ALBUMARTIST
Formatstring: %ARTIST%
Action #2
Actiontype 7: Import tag fields (guess values)
Source format: %TITLE%
Guessing pattern: %DUMMY%÷[%TITLE2%]
Action #3
Actiontype 7: Import tag fields (guess values)
Source format: %TITLE%
Guessing pattern: %TITLE%÷[%DUMMY%]
Action #4
Actiontype 5: Format value
Field: ARTIST
Formatstring: %ARTIST%÷'['%TITLE2%']'
Action #5
Actiontype 9: Remove fields
Fields to remove (semicolon separated): TITLE2
Note: Replace each special ÷ character with one space character.
I thought that was a very cool strategy. It looks like this temporarily makes a second tag called TITLE2, puts what's in [ ] into that, trims the title down to what's not in the [ ], and then appends the TITLE2 to the ARTIST, then deletes TITLE2. Did I get that right?
After messing with Foobar2000 a little more, it seems like a more useful way is to keep the TITLE pure, the ARTIST pure as well, and add a second ARTIST tag for the "featured" artist. I tried to change what you had suggested before, but changed Action 4 above to do this:
Format value
Field: ARTIST
Formatstring: %artist%\%title2%
Given that the \\ is the delimiter for a second ARTIST field, that's what I'm trying to do, but I think maybe I need to insert that character in a different way or something.
In essence, what I would like to do is:
Start:
ARTIST: DJ Tiësto
TITLE: You Are My Diamond (Feat. Kianna)
End:
ARTIST: DJ Tiësto\\Kianna
TITLE: You Are My Diamond
Any thoughts on how to do this?
Thanks!
EDIT:
I think I got it, I just had to do this:
Format value
Field: ARTIST
Formatstring: %artist%''\%title2%
That let Mp3Tag put in the \ as a special character. That makes both Mp3Tag and Foobar see the multiple ARTIST values.