[spetragl]

I'm trying to set up art for single mp3's in Kodi.
Initially I used mp3tag to add a "cover" image to the mp3 and Kodi picked it up as a "thumb"; that worked great.
Now reading the comments in the forum, it was mentioned that "fanart" might be added to a song.
So I went into an album, selected a single song, art and it showed just the "thumb" as available art types.
I added "fanart" and selected a wide screen jpg; that seemed to work nicely, filling out the screen.

Problem is, when I re-scan the album into the Library, it wipes out my "fanart".
The Wiki's I've read doesn't seem to indicate this is a valid art type for a song, and yet it works (mostly).
Is this some sort of experimental feature?

[black_eagle]

I'll try and answer this but I may well be wrong in parts!

Many people use the artist slideshow addon to show their art as it can do a nice slideshow for the currently playing artist.  However, if you are not using that then it's perfectly possible to achieve a similar thing by assigning different fanart to songs.  Kodi should show the fanart associated with the song rather than the artist or album fanart.  I tested that and indeed it does work.

Initially I used mp3tag to add a "cover" image to the mp3 and Kodi picked it up as a "thumb"; that worked great.

It does, but you are limited to just the front cover even if you have other art embedded in the files.  If you add local or remote art, Kodi will use that in preference to the embedded art in the order local art, remote art, embedded art.

Problem is, when I re-scan the album into the Library, it wipes out my "fanart".

This is due to the way Kodi currently rebuilds the music library.  Rather than just adding to the information that is already present, it deletes any current information and then reloads it from the tags in the files.  Means that your custom art will indeed be removed unfortunately.  There is a way to get Kodi to automatically pick up album art and artist fanart but I don't think there is a way to do that for individual song art.  Also, I don't think that you can export that info from the db currently and then re-import it again after a scan.

Your best bet really given these circumstances is to try to not rescan your stuff.  There usually isn't any need to do a full tag scan unless there have been changes to the Kodi core which have improved the data that Kodi reads from the tags.  Even then, unless it's a change that you particularly want (like the date stuff I added a couple of weeks ago) you can continue without the full tag scan and Kodi will work just fine, you just won't benefit from the changes.

So, best practice is really to get all your tagging in good order (this is a pain and takes ages if you have a decent library but is totally worth the effort in the long run) and then do a full tag scan just the once.  Stick with that until a feature or addition comes along that you want to make use of before rescanning else you will have to keep redoing your custom fanart for songs each time you do the scan.

Perhaps our music guru @DaveBlake who was instrumental in implementing custom art for the music library knows a bit more about it than me and can offer some sage advice.

[DaveBlake]

Fanart is primarily/traditionally artist art, just add it as artist art and all the problems go away.

Songs were not intended to have fanart, although with the expansion of art in v18 they can have it added manually or by addon, but will get amnesia if you rescan (as you have found). Add fanart for the artist, you can let scrapers find it or choose manually and store it locally,  and all will be well.