Hi
Miles - welcome to the forum!
I've looked at your post several times and see that there have been over 200 views but no responses - sorry, assume that music tagging on an iPad is not done much or even impractical? I went to the iPad App Store and did a search on 'id3 tag', and the first image below shows the results - I've not used these iOS apps so can give no advice - if not already done, you may want to download some of the 'free' ones and/or pay $3 for 'Metainfo' - if not sure, then look at the reviews. I also opened my music app on my iPad Pro to see if I could do any 'tag editing' in that app - could not find a way (unlike the music app on my Mac laptop).
NOW, do you have a 'real' computer? If so, a Mac is what I use as mentioned above - on that device, I have a great 'Tag Editor' (see second pic) that likely would do what you want - not sure about Windows options but sure they exist (completely converted from Windows to Apple in 2013). Well, about all that I can offer - hopefully you might get some responses after my post - Dave
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