How to add the same text to the tag for all files

For example, the tags are like this 'Cello Suite 1 - mvnt 1', 'Cello Suite 1 - mvnt 2' and I would like to add the text 'J S Bach : ' to every tag so the first one would look like 'J S Bach : Cello Suite 1 - mvmt 1' and the rest would follow the same format.


see the FAQs:

Thanks for the help.