Music 1.0.2.37 on Catalina 10.15.2 (19C57) crashing when anything new added to the library

so, using the above information, I managed to narrow it down to Music being terrible at managing duplicate files, thus causing the app to become unresponsive.

here's how I narrowed that down:

1) started a new Library

2) downloaded all purchased tracks

3) began adding media from previous Library, starting with letter A

in the process of doing this, I saw that Music did not have a way to understand that it should not add the previously downloaded versions of the tracks from iTunes, and would add them as (filename) 1.m4a

if those tracks were present, then trying to add anything afterwards would make the app freeze up.

SO

what I'm going to need to do is:

1) re-download purchased tracks

2) go to previous Music Media folder, search for folders containing files ending in (space)1.m4a, then delete those folders, cross-referencing with what is being downloaded into the new library.

problem persists as before, although I mis-stated: when material is added from finder or purchased from iTunes, it *is actually* added to the library, but <usic freezes and a beachball starts up. gotta force-quit Music and re-start to access anything added.

no dice. problem persists. I just tried downloading a purchased album from iTunes Store to the library, and Music is now spinning a beachball at the final step, "processing file."

the library file and all media is on an external USB. all permissions are correctly applied.