Please note that changes to Mac OS Notarization, an installer and application security signing procedure, may cause older audio plug-ins or hardware drivers to be incompatible or fail to install with Mac OS 10.15 (Catalina). This includes VST and Audio Unit plug-ins, or audio interfaces with custom driver software, whose installers have not been updated to implement the stricter requirements. Plug-ins already installed during a Mac OS update may be okay.
If you rely upon 3rd party audio plug-ins, please make sure the manufacturers have indicated compatibility with Mac OS 10.15. If not, consider installing any available updates prior to upgrading Mac OS, or postponing updating until those plug-ins are updated.