The "free" part of your search query might be referring to a trial or demo version of Native Instruments Bandstand. Unfortunately, I couldn't find any information on a fully-functional, free version of Bandstand that's available for download. Native Instruments usually offers a trial version or a demo of their products, which can be used to evaluate the software before purchasing.
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If you are on macOS Mojave (10.14) or older: The "free" part of your search query might