There is https://musicbrainz.org/doc/Copyright_Violation_Notice which is linked from:
Hang on, you’re violating copyright law by providing all my music online!
If you find your music listed in MusicBrainz it does not mean that we have access to or provide access to the music files themselves. MusicBrainz provides data about recordings, not the music itself.
If you still feel that we are somehow violating your copyright, you may report a copyright violation. However, keep in mind that the MetaBrainz Foundation is based in the US, a country where it has been established that factual data is not copyrightable.
If you believe that MusicBrainz violates your copyright, you may report a copyright violation. Please note that MusicBrainz provides data about recordings, not the music itself. If you find your music listed in MusicBrainz it does not mean that we have access to or provide access to the music files themselves. If you still think that we’re infringing your copyright, you must provide us with a link to where you can download the infringing copyright from our website. If you cannot provide us a link, we cannot help you.
Is it about the “artists” with one of the most entries as of 2024? The ones that were apparently also sending DMCA take down notices to Spotify for their own music? They also went after the Internet Archive to remove cover art they uploaded themselves…