Hi,

On the Mac, Band-in-a-Box (and update patches) always installs to Applications/Band-in-a-Box, so you'll need to fully install 2016, make sure it's updated to the latest build, then rename the folder to something like Band-in-a-Box 2016, then install 2018. If you want them to share RealTracks and Drums folders, you can delete those folders from the 2016 folder, then set up custom folder locations like John described above.

You'll want to make sure 2016 is the one that gets renamed, as if 2018 is installed anywhere other than Applications/Band-in-a-Box, update patches won't be able to find it.

Thanks
Kent
PG Music