> Music doubling up tracks

I’m running macOS 11.2.3 and subscribe to iTunes Match but not Music. Why is the Music app now duplicating everything in my library, and how can I stop it?

This is a not uncommon problem which can arise with an iCloud Music Library. The most reliable way to tackle it basically comes down to turning it off and back on again. You should do this when your Mac has a good Internet connection, and you should be able to leave your Mac connected and otherwise undisturbed for a while.

First turn off iCloud Music Library in the Music app. Once you’ve done that, sign out from your Apple ID in the Overview section of the Apple ID pane. Wait a couple of minutes to allow those changes to propagate through iCloud, then sign back in using the Overview in the Apple ID pane again. Once that has updated the pane, open Music and turn iCloud Music Library back on.

After some time syncing and updating, the behaviour of Music should have returned to normal. If you still have remaining problems, it may be the result of an account misconfiguration, so you should contact Apple Support so that they can check that and talk you through remedial action.

Problems with duping in iCloud Music Library are often solved by turning it off, signing out, then reconnecting.