GarageBand for Mac is a 64-bit application and works with 64-bit Audio Units plug-ins. 32-bit Audio Units plug-ins are not compatible. Checking with the developers of the 32 bit AU plugs gets you no where because most of them just say it is what it is especailly the plugs that are free and there are some excellent and simple to use free plugs. It there an application that can convert 32 bit AU plugs to 64 bit AU plugs ???