Catalina Music App
This just a word of advice. Make sure you back up all iTunes libraries before attempting to convert them using the Catalina Music App. Keep the backups for awhile because even though the library appears to have been converted correctly, it most likely has not. After many attempts and hours wasted I did manage a workaround and finally got my libraries converted, however there are many more bugs in this app - too many to mention here. This can't have been tested before the release.
iMac 21.5", macOS 10.15