First of all, the bad news is that you can’t do it directly. Gig Performer is a 64-bit application and so can only load audio plugins that are also 64-bit.
If you are using OS X and you have upgraded to Catalina (OS X 10.15) or newer you will not be able to load 32-bit VST, VST3 and AU plugins at all. Don’t even bother trying!
For earlier versions of OS X and some versions of Windows, there are currently some options. We’ve tried a few of them and the one we found that seems to work best is 32 Lives from Sound Radix. 32 Lives will find your 32-bit plugins and “resurrect” (their term) them so that they can be used with 64-bit hosts like Gig Performer.
It is not a free product but if you have legacy 32-bit plugins that you can’t live without but which have not been updated to 64-bit format, 32 Lives may do the job for you.
For Windows users, jBridge seems to be the most popular wrapper for VST plugins.
However, please note that Deskew Technologies, LLC does not provide any support for these wrappers so if your 32-bit plugins don’t work correctly, don’t call us! You will need to contact the wrapper developers for support.
There is absolutely no guarantee that future versions of Gig Performer will even work with these wrappers. We strongly encourage you to find 64-bit versions of such plugins as soon as possible.