Classical Composer Scripting Advice

Hi I wanted to add to the end of title the Orchestra, using the line posted here I did this:

Source From:
composer_lastname + \: + title, + \ § '+ band +\', title

into tags:
title

It worked like this:

Before: Bartók: Piano Concerto no. 1: I. Allegro Moderato
After: Bartók: Piano Concerto no. 1: I. Allegro Moderato § 'Deutsches Symphonie-Orchester Berlin’

But when “band” it’s empty it doesn’t work at all, how can I fix it? Thanks in advance the plug in it’s great.

Edit: I don’t know if it’s relevant but the tag is in a .flac archive. Would be different with an ID3 TAG?