Summary
Updating a large audio library could easily be a non-starter, either due to the time it would take to carefully match everything with Musicbrainz IDs or due to the risks involved with using quickie tools like Musicbrainz Picard. Plex and Plexamp could be great at music playback but the effort to get there isn’t worth it, presently.
What if there was a more efficient approach?
Instead of manually updating 10’s or 100’s of thousands of files across several or many terabytes of data, why not extend an existing Plex capability to knock the work effort down to a fraction of the time with comparatively little file I/O?
Support Musicbrainz IDs in .plexmatch files
Instead of modifying individual tracks, a .plexmatch file could simply be added to each album or album/disc# folder. All you need need inside of the .plexmatch file is the specific album release ID and the disc index. The artist, release group, and technical data are all implicitly known at that point. All that’s left for the Plex agent is to match the very limited number of files to the track IDs belonging to one release ID, which should be super easy since everyone’s tags are already meticulously perfect, right? Right. The amount of work it would take to capture those two Musicbrainz tags for every album or disc is trivial compared to current options.
Background
I’ve been building my digital audio library for almost 30 years now. My library is a respectable 4TB and growing. Like most anyone I see discussing audio library management, my tagging is thorough and meticulous and is organized to meet my preferences and use cases. I bought into Plex for its video library features and simply gave it read access to my audio library, not thinking much about it.
…until recently. I’ve now observed albums that are missing, mis-categorized, over-consolidated, and mis-identified. “Prefer local metadata” does not help. Additionally, I catch Plexamp’s Library Radio repeating songs quite often, which shouldn’t even be possible with >4TB of music and a good random seed. Mind you, this is all with good tagging in place.
I since discovered that Plex relies heavily on Musicbrainz for audio identification. Great! Presumably, 99% of the issues mentioned above would simply vanish if every track was perfectly updated with the correct Musicbrainz IDs.
That sort of undertaking is probably measured in decades. Seriously. MP3Tag could do it but at a rate of one disc at a time, if I want to do it right by measuring twice cutting once, it’ll take decades. Musicbrainz Picard is far too aggressive and would destroy all of the meticulous work I’ve already put into the archive. It’s not an option. I felt sorry for my test file copies after seeing what that thing did to them. 
If you’ve got a Napster-era thing going on in terms of tagging quality, sure, maybe that’s the right tool. I could write something to work specifically with my archive and all its nuances but that would still probably take a couple of years to build, and it would only help me. What about everyone else?
Forum thread reference that got me here:
