I’m writing this because I could not find this information anywhere else, and Apple Support with a couple different senior advisors were also not helpful on this front. This is just going to focus on getting Music to work, as there are plenty of articles on how to prepare and perform the overall downgrade from Catalina to Mojave.
Why downgrade from Music to iTunes?
I’ve been plagued with problems since upgrading to macOS Catalina. One of the main ones is the loss of 32-bit software. I upgraded because I had a virus infection on my iMac, and I wasn’t able to restore from Time Machine either, since the virus persisted regardless of how I did it, so I thought I might as well bite the bullet and upgrade to Catalina. I took steps to use Parallels Desktop to make a virtual machine to preserve my 32-bit software—even though this was not an ideal way to use it—but it was all too expensive and wasteful for me to repurchase it at this time.
But the most frustrating thing about the upgrade was the Music app. I found myself having to learn day after day how to work around the seemingly endless number of bugs in Music. I found bugs when scanning in CDs, in managing playlists, in viewing smart playlists, in menu options not working when you click on them, an inability to change Audiobook metadata, and on and on.
The last straw was when I spent more than an hour grooming the main playlist I use to sync music with my iPhone. The sync didn’t work, and I didn’t see the removals (to free up some extra space) and the new additions on my iPhone. I unsynced all of my Music and Audiobooks to start over again on the phone, to no avail: what actually happened was that all of the playlist changes on my iMac in Music were lost… the iPhone had became the master and blew away the changes on my computer.
So I decided to test the waters of downgrading by copying my library to another hard drive and seeing what would happen when accessing it from a laptop still running Mojave. Initially, it looked exactly as it did before I upgraded. I couldn’t see any of the more than hundred albums I had added since. The artwork wasn’t all visible. At first, I gave up hope. But then I started remember things I had done over the last fifteen years when doing other migrations and iTunes library management and wanted to see if I could easily get my library to be current again. Here are the steps I came up with, although I can’t guarantee they will work for your situtation.
The Steps, in a Nutshell
This seemed to get me back pretty close to where I was before I upgraded. I can’t speak to podcasts, TV, and Movies as I’m not a big user of those. But it terms of Music and Audiobooks, after performing the steps above, I was able to get back on macOS Mojave while preserving the music and playlist changes during the period I was on Catalina.
I think that for me Mojave 10.14 might end up being like Jaguar 10.2 (the last to allow booting natively into Mac OS 9), Tiger 10.4 (the last version to allow running Mac Classic software via virtual machine), and Snow Leopard 10.6 (the last version to allow running PPC software)—I’ll be stuck on it for a long time, likely until a new computer purchase is required for one reason or another.