I'm trying to re-write a bunch of tags on about 10,000 files on an SD card as I'm trying to shorten the album title to something a bit more car-friendly.

The album titles are formatted as 'Now That's What I Call Music! xx' where 'xx' is the zero-padded album number, 01 -> 99

Basically I want to do this (in pseudo-code):
IF LEFT(Album,29)='Now That's What I Call Music!'
SET Album = LEFT(Album,4) + RIGHT(ALBUM,2)

Whatever I've tried seems to always end up with all tags removed from the source files

Is what I want to do possible?