Reason Studios has announced that Reason Rack Plugin is now available as an Audio Unit. It is included in the free Reason 11.1 update.
“With AU support (AUv2 to be exact), Logic and Live 9 users on Mac can finally use Reason Rack Plugin,” notes Reason Product Manager Mattias Häggström Gerdt. “In this release, we have also spent time getting rid of some annoying bugs and making sure Reason 11 is fully compatible with macOS Catalina. Reason 10 will be Catalina-ready very soon too. And yes, you can now use the TAB key to flip the rack in Reason Rack Plugin!”
See the Reason site for details.