First and cheapest suggestion is to "unwind" this upgrade, at least until they resolve this forced incompatibility and come out with a solution for the millions of Mac users who don't want to let go of programs they love and use every day. I think this will be months, not longer. EASIEST way is if you had Time Machine backup running, then you can just go to an earlier update pre-upgrade, and stay there until they figure this mess out. If you did not have Time Machine running, then its a bit trickier, but still do-able.

https://macpaw.com/how-to/downgrade-from-catalina 

The second suggestion is to install Sierra or Mojave on an external Flash Drive or SSD drive. Here are a couple of different videos to show you how. Once you have done so, just install Piano Wizard and any other incompatible third party apps on that drive. 

https://www.youtube.com/watch?v=hOQwjht4kcE

https://www.youtube.com/watch?v=Vmo4242KFJI

To access that drive when booting, choose one of these options.

https://www.youtube.com/watch?v=9Px6tv29WP4

Third suggestion is to use a program called Parallels that allows you to run a "virtual machine" on the same hard drive. Unfortunately, this costs $79 (Its usually used to run Windows on a Mac, a much more complex process, but it easily runs Mojave on the virtual drive as well.)

https://tidbits.com/2019/09/18/moving-to-catalina-keep-your-32-bit-mac-apps-running-with-parallels/ 

Here is another article on that process: https://www.parallels.com/blogs/older-versions-mac-os-x-with-macos-sierra/

Cheaper than Parallels, but more work and "figuring out" is to use Boot Camp, a free partitioning software and create a partition that has an earlier version of Mac OS on it, and install all your 32 bit apps there to use when you need them. Its a little more technical, but not horrible, and, will not cost you anything. (This can also be done with an external hard drive that you install an earlier iOS on. Nowadays, you can even find flash drives big enough to run the older OS and programs on). More suggestions and "how tos" here: https://www.macworld.co.uk/how-to/mac-software/how-install-old-mac-os-x-versions-3679956/

We are searching for, and expect other solutions for this problem to be found, (Perhaps by Apple, complain and demand it, it is easy for them) and as those arise we will be glad to share them.

We are about a year from a major upgrade of our software, (for much better reasons than to satisfy Apple's move here), but until then, this award winning software is what we have right now.  

Hope this helped, check back with us if you wish as we are monitoring the situation to see what other solutions arise, from Apple or elsewhere.