the MTA looks very useful, but dont have a clue how to include this in mp3tag.
Is it as 'replace' or 'replace with regular exprewssion' or someother action.
CLose mp3tag
download the file above
move it to
%appdata%\mp3tag\data\actions
(copy this to the clipboard and paste it to the explorer's address toolbar, press enter)
You can with a little adjustment clone the existing action, and edit it slightly so that it removes the bracketts in the artists column, so then you have both options covered.