Just in case anyone stumbles on this, here is the solution to this problem:

Quote:
The BIAB plugin opens within GarageBand but freezes up when choosing a Style.


Do you have Band-in-a-Box installed on an external USB hard drive?

Go to Apple System Preferences | Security & Privacy | Privacy. Scroll download to Files & Folders and look for GarageBand - make sure that
"removable volumes" is checked. Also, you should see Band-in-a-Box listed there OR in the Full Disk Access section.
After that, quit GarageBand and re-open.

The first time any program needs to access an external drive (as well as some other things like Documents folder), it needs to request access (mac OS 10.15 and higher). If you say "no" then you need to manually set that in the Security & Privacy settings.


Andrew
PG Music Inc.