Currenty Overture 3 is customized for the GPO library exclusively. Gary and I have agreed that Overture 4 should be opened to other libraries, so I am in the process of making the changes. If you have any ideas, requests on implementing other libraries, etc., please let me know. You can send a direct email to firstname.lastname@example.org.
When Overture loads it looks for an instrument name list in XML files for each VSTI device and each device can have multiple lists or libraries, like full Kontakt. Each list contains information for instrument names, their transpositions, key switches, controllers, grouping, etc.. The appropriate name will appear based on the track's output assignment.
For example: If track 1 output is set to GPO, the GPO name list is used when editing expressions, name assignments, adding controller data. etc for items linked to track 1. If track 2 output is assigned to a different VSTi, its name list will be used for editing items linked to track 2, and so on. Each voice (up to 8) within a track can be assigned to a different slot/channel within the VSTi/player, but you can't have two voices within a track assigned to two different VSTIs.