[feature request] Multi value tag / metadata support (Genres, Artists, Mood, etc) !

Heya,

so there's a few threads requesting this:

https://forums.pioneerdj.com/hc/en-us/community/posts/203068319-More-than-one-genre-per-song

https://forums.pioneerdj.com/hc/en-us/community/posts/203051419--SOLVED-possible-to-give-one-song-2-genres-

etc.

The official reply back then here, that ID3 can not deal with this, is simply not true, there's many media/audio players who happily write/read/manage multivalue metadata...

Admittedly, this is not defined as a standard in ID3-2.3 (it was only explicitly declared as supported for ID3-2.4)... but the ID3-2.3 spec states that IF there's a need, a NULL character should be used in such cases and there's many a free media player (i.e. foobar & musicbee) which do exactly that to achieve multi-value genres, artists and many other fields. Some other players/media managers might only handle ; or / as separators (mp3tag, mediaMonkey etc)... but, it's easily possible (and imo the separator used should be user definable either way so users of foobar, mp3tag & Amarok are equally happy when coming to Rekordbox...), see

http://id3.org/id3v2.3.0

Also, flac, a supported format by Rekordbox, does have multivalue metadata support for yonks (and also the way it should be, via multiple single field declarations); see documentation:

https://xiph.org/vorbis/doc/v-comment.html

"Field names are not required to be unique (occur once) within a comment header. As an example, assume a track was recorded by three well know artists; the following is permissible, and encouraged:
ARTIST=Dizzy Gillespie
ARTIST=Sonny Rollins
ARTIST=Sonny Stitt
"

So, I would argue, especially in 2017 and if/when dozens of free media players & metadata managers do support this feature - a professional DJ software that wants to be the central DJ-ing hub should also be able to understand those multi value tags!

Cheers.

c.