Dear community,
I have a little compatibility problem concerning the CONDUCTOR field in MP4 files. I use MP3Tag to tag my audio files (of course 
) and MediaPortal as media center software. MediaPortal relies on taglib-sharp as tagging library. Unfortunately, the CONDUCTOR field written by MP3Tag is not read by MediaPortal.
In the tag field mappings documentation, conductor is not listed for iTunes, so I guess that MP3Tag doesn't treat CONDUCTOR as a predefined field. When I view my MP4 files in a hex editor, I see that MP3Tag writes a com.apple.iTunes atom having its name property set to CONDUCTOR.
I found out that MediaPortal is looking for a MP4 atom called cond. Thus I tried a custom mapping in MP3Tag from cond to CONDUCTOR, but this didn't help. I think this is because MP3Tag writes a com.apple.iTunes atom, and not a cond atom. One of the MediaPortal developers created a tag editor called MPTagThat which I used for problem analysis. It creates a cond atom on my files.
I don't know if there is a spec for MP4 audio tags, so I don't know how to store the conductor correctly.
Can I configure MP3Tag use cond instead of com.apple.iTunes?
If not, see this as a request for enhancement.