Here's my situation. I have tracks with the singer in the song title, like so:
Title:Yo soy el tango - Francisco Fiorentino
And the artist is the orquesta director:
I want to move the singer into the Artist field, like so:
Artist:Aníbal Troilo / Francisco Fiorentino
I've looked at old questions similar to this but they all involve completely replacing the destination field, and mention a Guess Values action that I can't find in the Mac version of MP3Tag. I tried using the $regexp() function but it just appends "%title%" to the Artist field:
Replace with Regular Expression Field:TITLE Regexp:$ Replace:$regexp(%title%," -\s(.*)\s$," / $1")
So I wind up with this:
It looks like %title% is being treated as a string literal rather than a placeholder for another field.
I think that would just remove the title and leave a slash followed by the singer's name. I don't know why $regexp() doesn't work in the Replace box, but I got the result I want using Import Tag fields. Thanks for offering the suggestion though!
$regex() is a scripting function that can only be used in Format strings. In the action of the type "Replace with regular expression" you have to enter just the patterns that in the end make up the regular expression.
And if in doubt, check the documentation: