AudioUnits(AU) on MacOS 10.15 [Catalina]
Unfortunately, in MacOS 10.15 (Catalina), third-party Audio Units may fail to work as you expect. A change made by Apple means that all software must be “notarized” by their security systems. Non-notarized software is entirely prevented from running on Catalina.
This change means many older third-party Audio Unit plugins will not work at all on Catalina. This issue will occur in any modern Audio Unit host, including Logic Pro X, Final Cut Pro X, GarageBand and many others. When attempting to use third-party Audio Units, you may encounter non-functional plugins, error messages, or other undesirable behaviors.
Next steps from third-party plugin developers
To get AU plug-ins working on Catalina, developers of third-party Audio Unit plugins need to issue updates. Once the software is properly updated, the plugins will again work as expected on Catalina. You should be sure you’ve got the latest versions for all your Audio Units.
If you have a third-party Audio Unit which does not work on Catalina, you should check with the developer to see if they have an update, and to request one if they don’t.