There are a couple of things to do to get Plex to use embedded tags from your media files before looking at online sources.
First, edit your Library and enabled the ‘Use embedded tags’ option. If using a Premium library, you may want to also set the Gracenote genre level to ‘None,’ as shown.
Second, arrange your metadata agents in the correct order. Make sure the ‘Local media assets’ agent is at the top of the list for Artists and Albums (I would do this for all subsections, Personal Media Albums, Plex Premium Music, and Last.fm):
In the Settings for the Last.FM agent, there is an option to use genre tags from Last.fm. I have never used this option, so I don’t know when it comes into effect, or if it will work in a Premium library. If you want Plex to prioritize your embedded genre tags, I suggest turning this option off, whether it does anything or not:
With these settings, Plex will prioritize sources of metadata like this (EDIT: I was informed in January 2017 that the order of 1 and 2 will be reversed as noted. Not sure of the effective version for this change.):
Embedded tags and imagesLocal artwork files (folder.jpg, etc.)
Local artwork files (folder.jpg, etc.)Embedded tags and images
- Online sources like Gracenote or Last.FM
In your ID3 tags, it’s important that the Album Artist (even if it’s blank) and Album title are identical in each file. If Album Artist is blank, the album will still be listed under the Artist’s name if the Artist tags are identical for all tracks. If they are not identical, the album will be listed under “Various Artists.”
In the case of multi-CD sets, It is also important that the disc number is correct in each file.
This screenshot is from EasyTag, the ID3 editor I use:
Once you’ve done all that, and especially if you had to edit ID3 tags to get there, you’ll probably need to do the ‘Plex Dance’ afterward to get Plex to read them in correctly. (The Plex Dance is a workaround for a problem that has existed in Plex seemingly forever. It should be embarrassing to Plex that they have such a major problem that has hung around for so long that the workaround for it actually acquired a name, but here we are.)
If you haven’t maintained your embedded tags, this may take a lot of up-front work, if you have a large library. Once done, it is much easier to just make sure the tags are right when you add new albums.