Perhaps because it’s already implemented?
Ups.. didn’t realized that..
Anyway, using a id3v2 tagger like “id3v2”, you should be able to do:
hmm.. I only found http://id3v2.sourceforge.net/
which is not able to set a TCMP or YTCP tag.
Okay… now I get it — automatically tagging songs as compilations if they sit under a particular folder name, like “various” or “soundtracks”, or “various artists”.