Even if this is possible, I would not recommend doing so. There would be contention for MIDI ports/devices, cpu resources, etc... Obviously you would have to have two difference audio interfaces connected. I'm betting you would run into additional stability issues as well. Think about it, a single crash takes out two players at the same time.
I noticed newcomer "Gig Performer VST live host" is designed to run multiple instances. I am going to try it out.
Forte, being more mature, probably has some features beyond Gig Performer, and I have a rack building investment in Forte, but running both might be worth a try to see if it works and solves my problem.
The Gig Performer VST knowledge base still states to use ASIO4All on windows...... that alone is enough to keep me away... yech!!
Re: "ASIO4All on windows"
I am testing Gig Performer on Windows10. I did not have to use ASIO4All. It works with my X32 Rack (32 channel USB audio card) with same drivers I use with Forte.
Early take on Gig Performer:
In general, Forte does the job for me nicely, so not ready to to become a Gig Performer "convert". HOWEVER, I could see also using Gig Performer in certain situations where wireless touch screen control via OSC on tablet/phone is desired.
Do you really need two instances of Forte? Why not have each player use dedicated midi controller(s), set to VST's in forte? That's what I do most of the time: run approx. 5-8 VST's played via different midi controllers, all at the same time.
So, if two key-players were to set-up everything in good order, if one changes the scene it should not necessarily affect the VST's the other one is using. Right?
Or am I missing your point?
Yes I have a secondary keyboardist (guitarist doubles on keyboards), and he has his own controller.
All works fine during the performance set, but in rehearsal or sound check, the other keyboardist is wanting to check sounds or run through his parts.
It does feel weird to him that he has to ask me to switch the scene. People are used to being able to switch their own sounds.
Once my "super-computer" (64 gig memory) is on, it would be nice that the VST host can function as two or more independent racks. So the multiple players can feel in charge of their own rack.
"if one changes the scene it should not necessarily affect the VST's the other one is using"
But no, that is my point, changing scenes DOES affect the other player , right?
So, answering your question regarding changes: not necessarily!
Several details here... Forte is a live rack. Indeed, one rack, though with a massive amount of possiblities. If your guitar player changes his settings, that of course should not influence your synth settings, and vice versa. But you would like to be able to do so here...
Don't get me wrong: I've been using Forte for several years now, but I'm no pro user, so I could be wrong on points... Check MikeG for the specifics, he's the man-with-the-plan for everything, in my experience.
I find Forte to be massively powerful (I have no idea of Gig performer for that matter). It has the ability to change settings really fast from scene to scene and from VST to VST. Each scene can be set-up like you want/need it to be.
I've set up scenes in which controller (A) is continuously assigned to Kontakt Session Horns, and three others controllers (B-C-D) are controlling other VSTs (at the moment Korg M1, wavestation (multiple instances), poly6 (multiple instances), MS20 (multiple instances), Prophet5/VS (multiple instances) and energyXT) when/if necessary. And while I'm toggling through scenes, Kontakt (with controller A) does not change (or only minor changes in the horn set-up if necessary). To do this, see:
Scene commands. This way, I'm confident that whenever I hit controller A, the horns are present. Maybe you could translate this into your set-up as well. Maybe this could work for you too.
I understand it's for the sec.key player and during rehearsals only. Likewise, I've been trying to see if it's possible to have two midi CC controllers perform a scene increment. Set-up is via Global midi automation, but it seems that isn't possible. Only one midi automation adjustment is possible.
But, have a look at this page, for it has some briljant solutions. It does mean some more programming... But it could be a simple solution for you.
While gigging/rehearsing for several decades now, I've been looking for external solutions on situations which, in the end, most of the time I was able to solve internally, because Forte can do/be so much. Most of the time there are already fixes for your issues present in the settings. Like I said earlier: MikeG is the man here.
So, coming to my earlier question: how necessary is the scene changing for the sec. player?
Good luck with the programming!