Thanks Bob! Somebody suggested this tag editor which looks pretty good: Mp3tag - Thanks for using Mp3tag
From what I understand, though, I need to burn / embed the IRSC into the file, rather than just tag? Will investigate the options in Elements as well. I’m also wondering about whether the file should be ID3 tagged? I’m not really sure how radio stations collect their IRSC data to report air-play (which is why I want to add the IRSCs)…