Five weeks ago all of my music (iTunes/Music) playlists went missing.
My music was in my library, but my playlists were all duplicated, in name. One playlist had all of my music and the other was empty. After opening and closing the macOS Music app several times, the duplicate playlists remained. So, I deleted the empty playlists... all 85 of them. Over the course of the next ten minutes, all of my playlists disappeared on my iPhone, iPad, TV, and HomePods (thanks to iTunes Match, Apple's music cloud syncing service). My playlists remained on my Mac, but clearly there was a problem, so I called AppleCare for support. While I was on the phone with them, all of the playlists disappeared from my Music app on my Mac. That's nearly two decades of curated music that went missing an all of my devices.
The senior Apple advisor I was talking to was extremely sympathetic to my issue. Over the course of a couple hours, we tried a number of different things, including recovering my music library from my Time Machine backups. But, to no avail. It seems iTunes music libraries used to get backed up via Time Machine, but the new macOS Music app, released in October 2019, doesn't backup the library.
Over the following few weeks, things were a mess as I was transferred around amongst different senior advisors throughout AppleCare. There was a lot of confusion over the proper description of the issue in my trouble ticket. Many were describing it as "missing music" instead of "missing playlists."
Throughout these steps, there were times when I could restore an iTunes music library playlist into the macOS music app. But, while the playlists remained, all of the music in the playlist would quickly disappear (within in a minute or two) as iTunes Match thought the playlists were stale, and deleted them.
Playlist SolutionI finally figured out a somewhat tedious workaround to restoring my playlists that AppleCare confirmed with me as my best option on our next, and final call.
1. Uncheck Sync Library in macOS Music General preferences.
2. Close the Music app.
3. Restore my last iTunes music library backup, from September 2019.
4. While holding down the Option key, open the Music app and choose the old iTunes music library. My playlists appear, although, without any songs.
5. Choose each playlist, individually, and choose File –> Library –> Export Playlist. (I had to do this 85 times.)
6. Once complete, I went back to my Music General preferences in step one and checked Sync Library (and then my playlists disappeared).
7. I then imported all 85 playlists, one at a time, by clicking File –> Library –> Import Playlist. Here's what that looked like.
One gotcha was that, when I double clicked on most songs in my playlist, a modal window popped up saying that Music couldn't locate that song. Once I clicked cancel, to dismiss this modal, all was fine.
The other gotcha was that I lost any playlist updates between September 2019 and the beginning of January. Luckily, that was a small amount of edit, especially compared to the last 19 years.
On 3 Jan 2020, I lost all of my macOS Music playlists. That's 19 years of curated music that was wiped out on all of my devices since iTune Match syncs my music.