This does bring up the issue of non-binary narrators. Em Grosland uses both he/him and they/them, so Male Narrator is appropriate, but I'm sure there are voice actors for whom neither label is appropriate. (Incidentally, Em is the narrator for A Psalm for the Wild-Built, which is the book equivalent of a warm cup of tea on a rainy day and I recommend it highly.)
Do any libraries maintain a Non-Binary Narrator heading? Or do you not include either? Does anyone have a good standard operating procedure here?
As with so many things in life, "it's complicated." These two headings exist because patrons with hearing loss sometimes can't hear voices of a certain type as well (or at all) as others. NLS' solution was to create these two headings to use as an exclusion. I can honestly say; I have no idea what would be sued instead of male or female. "Low" or "high" doesn't work but is getting there.