I can't edit the narrator field on audiobooks.

Looks like this is a non-editable field - set by the publisher but can't be modified by the user (at least within iTunes). I'm only seeing this populated in some audiobooks that I've purchased from Audible, in other cases the field is there (for individual audiobook files) but doesn't even have a control to enter a value for it.

It doesn't appear in any other media kinds, and isn't even displayable in the columnar "Audiobook List" view - the two usual "tricks" to make some metadata elements editable. May be worth submitting feedback to Applesuggesting that making this user-editable would be a useful enhancement, though since many audiobooks are DRM protected it may not be possible to make this change.

I tried using a couple of tools:

• Chapter and Verse(a useful utility for converting/consolidating mp3 and m4a files into m4b format audiobooks) doesn't have a Narrator field in its metadata editor, at least when opening an existing .m4a file. I'll check and see whether this is available when converting from mp3 or m4a, though I suspect that it doesn't ... its help file suggests that it can retrieve narrator information from Audible but puts this into the iTunes Composer field - which isn't accessible in iTunes 12 when the media kind is Audiobook
• Foobar2000 (though primarily a media player, does have powerful metadata editing tools) did allow me to add and populate a NARRATOR element, but this didn't show up as the Narrator value in iTunes.

I suspect that - like a number of metadata elements for other media kinds like podcasts and TV Shows - iTunes reserves this field for publishers only and will not make it user editable.

Just to confirm, even though Chapter and Verse can download "narrator" metadata it actually puts this into the iTunes Composer element, not Narrator.