Is there any documentation on how foobar2000 applies its album art? I have a CD that has an artist and two contributing artists on several of the tracks. I have art for all three artists attached to the music files. But no matter how I configure the art, I cannot get the correct picture to associate itself to the correct artist.

I have gotten the following three scenarios so far with my experimentation:
1. The "Artist" art appears; the "Contributing Artist" art does not appear.
2. The artist and one contributing artist get their photos switched, and the second contributing artist doesn't get the photo.
3. The artist and two contributing artist all get their photos swapped.

If the music files has three artist and contributing photos attached, foobar2000 WILL show all three photos in some way, so it can accept this scenario. It just does not do it in any (so far) predictable way.

I have two questions about this:
1. Is there any documentation about how to add album art to music files for the Contributing Artist?
2. Has anyone done any successful experiments to add correct art for both the Artist and Contributing Artist photos?