Music/iTunes syncing with iOS devices is indeed slightly screwed. From my diagnosis, it is because of iOS 13 update and has little to nothing to do with macOS Catalina update.
Connect your iOS device to Mac.
Go to your device syncing app:
iTunes for pre-Catalina; and,
Finder for macOS Catalina.
Select the device you want to fix your music library on....
To simplify when using iTunes Match, your phone or other device, connected to the internet, can play "your" music from Apple's Servers. Apple scans your physical music Library and then "Matches" the songs to songs they already have.
This means that if Apple has a song on their server that "Matches" a song in your physical Hard Drive music library then it ...
Click on the first song in your library.
Scroll down and shift-click on the last song in the library.
Now everything is selected.
Two-finger tap on any of the songs to show the context menu
Select “add to playlist”.
There are three ways (that I know of).
The first method is going to System Preferences -> Users and Groups -> Login Items
and clicking the - button when selecting an application to remove it from startup.
The second method is to right-click the application in your Dock, then uncheck Options -> Open At Login.
The final method is going to Finder, ...
I have gotten confirmation that yes ratings and play counts both transfer to OS 10.15. I was asked for the source of my information: I checked with Joe Kissell the publisher of the Mac Take Control books and he check and confirmed with Kirk McElhearn the author of Take Control of Mac OS Media Apps. Both said in emails that both the play count and rating ...
Any of the above may apply, but this solved mine;
As soon as I unplugged from power, the buzz went. Nothing to doo with ground loops, or bad connectors ( even though 3.5 mm plugs differ surprisingly ).
The answer was that the laptop Battery was long overdue for replacement. When power is put through this for charging, you get the hum. I have about 40min of ...