I'm using this Regexp to get a more natural capitalization. The only problem is that words in teh beginning of a parenthesis should be capitalized, even if they're in this list. The typocal example would be Artist - Title (the Blah Blah Remix) where of course the "the" should be capitalized.
I have absolutely no knowledge in these scripting but would very much appreciate any help!
If you are not satisfied with the result of the action that you described in the OP, then add another action of the type "Tag Conversion" and enter the "(" for characters that denote a word boundary .
You have to enter all characters that do this, including space, comma, full stop etc.
You have to adapt Step 1 from the given proposal by user "Juozas V" to your own needs.
In the first action "Case conversion" you have to define one or more character/s within the edit field "Words begin from/after any of:", which should be uppercased.
In your case this will be the one character for the "open round bracket".
Within this edit field there can be defined more than one "trigger character".
You are still using Mp3tag Version 2.65a?
Consider updating to version 2.81.