Trouble with Halion Sonic (not SE version) in Dorico 4 Pro

From the Dorico 4 Version History PDF:

Universal app on macOS

Dorico 4 is now a Universal app, which means that it runs natively on both Intel- powered Macs, and on the latest Apple silicon Macs, such as the M1 MacBook Pro, iMac and Mac mini. If you have an Apple silicon Mac, Dorico will run as a native application by default.

VST plug-ins. When running natively on Apple silicon, Dorico can only load VST plug-ins that can run natively as well: it is not possible for Dorico running natively to load VST plug-ins running under Rosetta 2, the technology that allows software built for Intel-powered Macs to run on Apple silicon Macs.

In addition, there is no support for VST 2 plug-ins on Apple silicon, so when running natively on Apple silicon, only native VST 3 plug-ins will appear.

If you still rely on one or more VST 2 plug-ins, or if a VST 3 plug-in you rely on is not yet available in Universal format, you can force Dorico to run under Rosetta, which will allow VST 2 and Intel-native plug-ins to be loaded, though at the expense of slower overall performance.

To force Dorico to run under Rosetta:

  • Quit the application if it is running.
  • Locate Dorico 4 in your Applications folder.
  • Select the icon and type Command-I to open the info panel.
  • Activate the Open using Rosetta checkbox.

When you next start Dorico, it will run under Rosetta.