Catalina Music loses equalizer setting
I eventually found a workaround.  I believe that the problem is that each new song reverts to whatever is the default equalizer setting.  

The workaround is to set an equalizer preset individually for each song.  You can do this for several songs at once--all of them, if you want--by highlighting the songs, choosing Get Info, going to the Options tab, selecting an equalizer preset from a dropdown towards the bottom of the window, and then saving.  That is what I am doing now.  Catalina Music is a lot less annoying now (but still annoying in some ways!).