How to copy MP3 metadata/tags created in iTunes?

[ohrenkino]

@pomozki

sorry but if one of the mods here can answer this for me, I'll make a small donation to the site -
I'd like to

1. copy my composer field (it's full of numerical values, all different) to Disc Number
   then
2. copy my comments field (full of text and numbers, all different), to Composer

would my changes automatically show up in iTunes?

You could have saved the money if you had read the FAQs ...
If you want to copy the values of one field into another, please refer to
/t/967/1
This will replace the existing contents of the target field with the data from the other field.
If you want to append e.g. DISCNUMBER with the contents from COMPOSER then have a look at the FAQ
/t/967/1
Only enter %discnumber% instead of "xyz".

And as a reminder: this is the MP3tag forum - iTunes functions should be discussed in an iTunes forum, I guess.
I can only report you my experience: no, of course not, your changes will not show up "automatically" in iTunes. The changes will be in the files, allright, but iTunes has a mind of its own on when it reads the track data anew. There are various tools and scripts on the market that will iTunes force to update the data but none of them works "automatically".
Actually, the easiest way would be to delete the entries from iTunes and reread the folder(s). Rereading without deleting does change a lot.