Many of the less common predefined ID3 frames can be considered as suggestions for the program developers. Each developer can pick what seems appropriate. I am not aware of any single program that supports each and every ID3 v.2.x tag frame that is defined in the informal ID3 v2.3 and ID3 v2.4 standards.
TORY is not one of the currently supported tag frames and there is no way to read or write it unless the JRiver developers decide to add support for it.
The Mood library field is linked with the MusicMatch Mood ID3v2 comment frame and it works as intended. This Mood tag was introduced in the now discontinued original MusicMatch Jukebox program many years ago. The JRiver developers added support for it and several other, mostly proprietary, MusicMatch tags because many former MMJB users requested support for their existing tags.
Thank you, Alex B, so much for the prompt and clear - but disappointing - answer!
May I try your patience with another question? I am a new user trying to evaluate if MC is the music management software for me. I have discovered some great features so far, but the ability to read, and preferably also write, my most important tags is essential. I have a rather large library and retagging therefore means a lot work, which I am hesitant to invest especially if this means that tags that are important to me will deviate from the standard.
If I, in MP3Tag for instance, copy the contents of the TORY tag to a tag which I name, say, TRACKYEAR, then MC could import that tag (TXXX Trackyear) and write back to it (bot not the original TORY tag) if I create a library field in MC named "Trackyear"?
And now this question as a hopefully final test of your patience (and yes, I know that the question is also off topic): An absolute requirement for me is that my primary music management software can read all information stored in i.a. ARTIST and COMPOSER tags, which are essential. I have become aware of the fact that MC as yet does not support reading and writing of multiple ARTIST and COMPOSER tags (Vorbis comments) in one flac file. MC only reads one of the ARTIST and COMPOSER tags in one file. My question: Does MC _always_ read the first of those tags in the file as displayed by MP3Tag?
I like the functionality in MC, once the information has been retrieved, so much that I am considering to find a way to use MP3Tag to copy the information in the subsequent tags to the first one separated by a separator character (and yes, I do know that MC as yet does not support a list type Artist field), but this would only work if I can be sure that MC always reads the first tag. A follow-up question would then be if you perhaps know of a script for MP3Tag that can do such copying. By searching the forums I have found a thread with an example of how to move, not copy, multiple tags to one tag.
I have tested and found that MC is "well behaved" when writing tags in that MC does not seem to touch ARTIST and COMPOSER tags (Vorbis comments) that MC has not read, i.e. a change in MC of the ARTIST tag read by MC is only reflected in that ARTIST tag and the other ARTIST tags in that file are not deleted or altered in any way. Can you confirm this?
And finally, just a comment as regards the Mood field: It seems rather odd that the tags written by a software discontinued for years is allowed to be imported into a field in MC which is blocking users of current tagging software (MP3Tag) to import tags retrieved from a very common tag source (AMG)... But as I said the Mood tag is not particularly important to me. BTW: I was a user of MusicMatch, but I have by now cleaned up my tags from that experience.