As is well known, multi-value fields are handled quite differently in different programs with tag options.
MP3Tag shows them in the list view and in the tag panel separated with "\\", in the extended view as 2 separate tag fields.
Other programs use different separators.
Specifically, I am currently concerned with the interaction of Mediamonkey and Mp3Tag. I mainly use Mediamonkey with the very handy script "Lyricator" to automatically add content to the "UNSYNCEDLYRICS" field.
However, there are always side effects, in this specific case with multi-value fields.
If an MP3 file has been provided with a multivalue field by MP3Tag, this Mediamonkey displays separated with the separator "; ", e.g. "Content1; Content2". If Mediamonkey now saves the file again because something was changed in a tag field, Mediamonkey probably saves all tag fields again and changes the multivalue fields. Mediamonkey distinguishes between tag fields that it believes are multivalue-capable and those that are not, e.g. ARTIST (not) and GENRE (capable). MP3Tag probably doesn't know any difference in this regard.
After re-reading in MP3Tag, there are no longer any multi-value fields in any case.
With ARTIST MP3Tag shows the diffenernt artists separated by the separator "/", with Genre the different gernres by the separator "; ". Th extended view no longer displays multiple fields. So the multivalue fields have been eliminated.
Since I let the aforementioned Lyricator script process larger parts of my collection at intervals, as I said, I am almost forced to constantly keep an eye on multi-value fields in order to correct them later.
Irrespective of the question of which software is behaving in a non-compliant manner, I am concerned with the question of how I can circumvent or deal with this annoyance with the help of MP3Tag. I don't want to do without the Lyricator in Mediamonkey and I don't think it's realistic to convince the programmers there to take a different approach.
You have not really said who you think should be the pacemaker.
This looks to me as though you cannot use multi-value fields in your favourite player.
So, the only way would be to merge the duplicate fields and use the slash as separator for ARTIST and the semicolon for GENRE.
There are actions for that.
In the end It did not really help but it inspired me to have a closer look at the mentioned option for the separator and to install the new version 5 of Mediamonkey.
Mediamonkey 5 does not have this problem anymore. When it writes to the file it does not change the multivalue character of the fields as version 4 does.. The defintion of the seperator semms to be only relevant for the display inside Mediamonkey.
My favourite addon "Lyricator" does not work in Mediamonkey 5.
So the only solution at the moment which I can think of is to filter for unwanted slashs and semicolons after the use of Lyricator and to correct the content.
Thanks again for the tip that encouraged me to do more testing.
I was wrong in my assertions that Mediamonkey 5 no longer has this problem.
Mediamonkey 5 can also use ID3v2.4 and has set this as the default. I didn't change this setting in my test because I didn't look at the options.
Setting again to save ID3v2.3, the same problem with incompatibility of multivalue fields occurs. So it is the setting of ID3v2.4 for saving that made it keep the compatibility.
MediaMonkey (v5) without all the great and highly needed plugins is not worth the money IMHO.
They decided to begin from scratch and use a completely different scripting language. Instead of make it compatible to all existing addons and plugins, the MediaMonkey developers blame the plugin writers
The fact that Addons aren't available is up to the developers of the Addons
At least they admit:
One of the big problems is that MM5 uses a different scripting platform to make it read for cross-platform capability. This means a lot of work to update a script.
No one with more then a few CD's in his collection will ever use MediaMonkey on a smartphone or a game console or Linux or Apple, but "platform capability" sounds cool - for marketing people selling a "new" product.
MM4 with his database was a good thing, even for large collections. The SQL-Addons for example were a great help to find some edge cases in the own collection.
MM5 looks nice, but lacks most of the important addons. And they will never be ported to the new scripting system.
I will never understand why Peke & Co. made this decision the way they did.
Going a little off-topic here. But I would not make a decision on how I manage my metadata for my music library strictly based on the capability of one player's features. There have been far too many come and go over the last 20 or so years that this cannot be dependable. I (try to) keep to the key fields that can be commonly found across all platforms. At least with these in place, I can depend on my browsing habits to be consistent regardless of using a PC, DLNA browser, or mobile device on IOS, Android, or any other OS. All other less common fields including the sort tags I use are under the "nice to have" category for me, but without them I can still get by. Who knows what will come in the next 20 years.
I don't use Mediamonkey as my regular player. I started to use it about 14 years ago as a taggger and database before I got acquainted to Mp3Tag. The main reason why I still use it is because of the plugin "Lyricator" which I like very much.
I don't see metadata only from the view of a player but also as a "database" of information I want to keep.