Save Tag but Retaining Unspecified Fields

is ther any way I can add or change some tag fields in multiple files while leaving fields I have not specied (ie fields I've left blank in MP3Tag) unchanged in the files.

Alan Lloyd

Yes you can add content to or change content within an existing tag-field without changing other tag-fields.
Yes you can create a new tag-field by writing some content into a newly named tag-field.
As I understand Mp3tag ... it does not change non existing tag-fields.

Open the dialog "Extended tags..." and investigate what tag-fields are currently stored in the one selected media file.

Please elaborate what has led you to your question.

DD.20121119.1310.CET

The default behavior of Mp3tag is to not change any fields that you're not addressing, so you should have to do nothing special to get this behavior. But if you're not editing a field, you wouldn't leave it blank, you would leave the existing value.

Note that in the Tag Panel drop-down boxes, any time you select multiple files and the content of a field is not the same in all files (typically, TITLE and TRACK), then it will display "". Only if you alter this or set it to "" (or an empty string) will any values be changed. Same thing in the Extended Tags.