I am not quite sure what you mean.
The list of genres is defined by the standard and some enhancements, see e.g.
ID3 is a metadata container most often used in conjunction with the MP3 audio file format. It allows information such as the title, artist, album, track number, and other information about the file to be stored in the file itself.
The ID3v1 series, in particular, stores genre as an 8-bit number (therefore ranging from 0 to 255, with the latter having the meaning of "undefined" or "not set"), allowing each file to have at most one genre out of a fixed list.
Genre definitions 0-79 follow the ID...
If you want to add user-defined genres, see File>Options>Genre
If you want to add a drop-down list with user-defined entries: there is no such function in MP3tag, see e.g.
Hi, and thanks for the followup.
Yes, I think the reason for these various posts is what I was pointing out: That people are now using more custom tags and they want a flexible way to keep track of all the ways they're using those fields.
Here's the problem: mp3tag assumes the user will be fine with just seeing whatever tag values come up contextually when viewing a certain group of files. But what if I've got 30 or so values that I want to choose from, but which don't exist in the particular…