Ohrenkino, you raise a good point with the "/". I do use the " / " and, as I recall, I believe the reason why I added the spaces is for bands like AC/DC. I think I went with the "/" because some programs used it as a separator, and WMP may have been the one that convinced me, even if I do not use it as of yet.
In the CD Ripper from dBpoweramp you indicate multiples with ; which means that the program writes multiple fields but the ; itself is not written into the metadata, it's just an indicator in CD Ripper.
In Mp3tag ; is not an indicator so it will be written into the metadata in a single field.
I'm not sure what happens in the Audio Converter from dBpoweramp when you load your already tagged FLAC files, but since ; is used as an indicator by dBpoweramp I just raise a warning that it might be interpreted as an indicator and thus split the field.
Since you have dBpoweramp you could test this with some sample files, to be 100% sure what actually happens.
If you test, be aware of the difference between "; " with a space and ";" without a space. You should test both variants in dBpoweramp but also in your player.
As vilsen suggested, I did test using a ";" and a "; " with the space and then I converted the files with dbPoweramp. It did not seem to do anything to the tags. They were exactly the same in Mp3Tag. I did import the converted files to Foobar. Interestingly, it did not split the fields.
So I experimented with all the different variations using / \ and ; either with no spaces, a space before and after, and space before, and a space after. None of them split fields converting with dBpoweramp. They all read as just one field when I reimported them into Mp3tag. With no difference in the tag at all. When I imported them into foobar, the same thing happened. Nothing got split into fields they all stayed in the same GENRE field.
I experimented further using "//". When using these separators, Mp3tag immediately created duplicate fields splitting the fields in the extended tag panel. Interestingly, in the columns, all the values were displayed as one in the GENRE field, with the "\" separating them, but in the extended tag panel they were split. I guess that makes sense.
When I converted these files using dBpoweramp into ALAC and WAV to experiment with different formats, I came across another interesting result. When viewing them in Mp3Tag, the ALAC file was treated the same as the FLAC, with split fields for each GENRE and displaying as one under GENRE in the columns, but the WAV files now had a ";" where the "\" existed, and the fields were NOT split. They were all in the GENRE field in both the extended tags and in the columns. Mp3Tag seems to realize that in the windows environment the ";" functions like the "\" does in Mp3tag and, consequently, supplants them. Pretty neat.
When I imported these three files into foobar another interesting result followed. In the GENRE column in the playlist view the "\" and ";" now were displayed as separated by a "," in the ALAC/FLAC & WAV files, but in the properties panel they still all displayed semicolons (";") in lieu of the ",". I guess Foobar uses "," as separators?
I would have thought it would have split the fields for foobar either with the "//" or the ";". I thought it used the ";" as a separator, but apparently not, or maybe the "," I saw in the playlist panel signals the presence of multiple values in the GENRE field. But, again, in the properties, the files displayed the semicolon (";").
When I imported the files to iTunes, the ALAC files using the "\" separator were truncated and only displayed the first value in GENRE, prior to the first instance of "\". This was not surprising as iTunes does not handle split fields or multiple values (among many other things, damn you Apple!). The WAV files had no tags attached to it when imported to iTunes for some unknown reason. I really did not care, because I do not use .wav, but that was unexpected. I double checked and the tags were still present in Mp3Tag, just not in iTunes.
So Mp3Tag must be signaling something special with the \. Obviously it does something within Mp3Tag itself. It seems to know that the "\" should be replaced by a ";" for WAV files. It seems to know to convert the ALAC to the same format as the FLAC files, splitting the fields when viewing them within Mp3Tag but keeping the conjoined when viewing in other programs. I would have thought it would have split the fields for foobar. I thought it used the ";" as a separator, but apparently not. The presence of the "\" did trigger then change to the "," in Foobar but, again, no split field.
So which separator to use? I think I will stay away from "\" because it truncates the values in iTunes, which, unfortunately, my player of choice because it is so universal and has so many apps, airplay and control with the iPhone and apple watch. I have tried to break away a few times, but they keep draggin me back.
I could stick with the "/", but adding the two blank spaces " / " to avoid the AC/DC problem can prove limiting when trying to fit all the artists in an orchestra in one field that I believe is limited to 255 characters.
I may just switch to the ";" with no spaces. It would be especially if foobar, the player I want to eventually move to would actually treat the ";" as a separator, but the only thing that may signal something to foobar is the "\" but since it can have deleterious effect in iTunes, I will refrain from using it.
So, ";" it is, unless someone can point out some drawbacks. I plan to use no spaces and just the ";". If anyone can see how that may present a problem I would appreciate you mentioning it.