Compilations and modified titles to include artist in brackets

[ohrenkino]

This is roughly handled in the Howtos:

Actions and batch-operations

How to append the string " xyz" to the content of a tag field? Create a new action in an existing action group and choose Format value as action type. Field specifies the tag field the formatting rule should be applied to. Format string must have the field placeholder for the field selected above and the string which should be appended. Example: If you want to append the string " xyz" to the current value of the comment field: Action type: Format value Field: COMMENT Format string: %com…

In your case, I guess,
Action of the type "Format value" for TITLE
Format string: %title% (%artist%)
Or give an example of what the string looks like before and what it should look like after the treatment.