You don't use Hauptwerk in Aria. It has it's own VST player that you need to setup in Finale. Which version are you using?

I am using 2014.

The only Hauptwerk I see in GIfF is the "All Stops" version. There are no provisions even to combine stops via MIDI channels in Aria as you might do with the GPO5 version (with considerable work-around effort).

As William suggests, the specific Hauptwerk with its own player would be the best way to control the different stops available.

It looks like Hauptwerk installs the plugin in C:\Program Files\Hauptwerk Virtual Pipe Organ VST Link Plug-In on a PC, so you'd need to add that folder in the Plugin setup under Audio/MIDI. Don't remember how the menus are setup in 2014. Be sure to use the 32bit version.

I trying to understand this. I think I need to add that file you mentioned to the folder in the plug in setup - under audio/midi, I will try that. THANKS

I think I found the VST plug in but it wont copy to the directory or show up in  the list.

I mean I have no idea how to get that folder into Finale

I don't remember exactly how 2014 is set up, but it will probably be under Audio/  -  MIDI Device Setup

If you have an instance of Hauptwerk open, it should show up as a device in the score manager. You'll have to load your organ and do your stop management in Hauptwerk. There should be a way to do expression pedal/pistons/stop changes via MIDI messages, but I don't know how that's done, on either end.

Since this is a 2-year old thread, I think we can assume that they either solved it, or moved on...