Tag doesn't change in Itunes

I just started using Mp3tag. Purpose is to change album info to organize differently in Itunes. When I changed directly on Itunes often reverted back to what was,

So I am trying to group albums different than tags are. For example I would like to group Yo Yo Ma and others as classical instead of by their name. I therefore change album artist from Yo Yo Ma to classical. Similarly change Paul McCartney to The Beatles under album artist and save.

On hard drive and subsequently in Itunes no change. Still Yo Yo Ma and Paul McCartney, for example. What am I doing wrong?

Thanks

see e.g. this thread:

Or what are we talking about? Filename or metadata tags like ARTIST, TITLE?
What should change on a hard drive?

Are you hitting save when you make the changes? Everything should change. Make sure you exit out of itunes because I have noticed that if I have itunes open, it does seem to revert the changes at times.