Hmm, that’s interesting. I tried it with some cds that I had to hand (and with a silly misspelling to make it obvious if it was working):
$set(album,$rreplace(%album%,\(Genius of Modern Music|The Eminent Jay Jay Johnson\).* \([0-9]{1\,2}\),\\1 - Voloom \\2))
…and this worked for me. So possibly it’s a matter of when the scripts are applied? There’s a previous forum thread on that issue.