I (we) just started using a second instance of GP4! I think the main motivation was to reduce the load time for our drummer’s gigfile, which was getting cluttered up since I’ve been adding more synth plugins. Instances of Pigments, in particular, take longer to load. So I copied the song rackspaces that use synth plugins (I’m up to 6 now, using Reaktor, Kontakt and Pigments to augment or replace my Nord Modular G2X sounds) into my own personal GP4 instance. Now the drummer’s gigfile, with its 40 song rackspaces, loads nice and quickly, and my continuing expansion into virtual synths won’t affect him.
The other motivation was that the drums were starting to have occasional dropouts, distortion and note pile-ups at gigs, and it was back to the drawing board to find and disable more macOS processes that could be getting in the way of real-time performance (and I’ve since upgraded to Big Sur, see [blog] Optimize your Mac for a gig - #13 by therealgps). Having a separate drummer’s instance of GP4 makes it easier and faster to quit and restart his gigfile.
I set up the Mac Script to load both instances, and also exported all settings in each instance so I can easily import them when switching to the audio interface we use on stage. This is all great stuff, thank you Deskew!