Hi Dan

I will use Kontakt as an example:

Assuming you have a suitable Flute & Brass sound set up in a Multi, then you can just switch between them using the bank/program change instruction the same as if using the on-board sounds, any sound modifications can be done automatically by cc codes when you select the sound. (I name my voices in the VST Host the same as the VST sound (For convenience) and program them with the appropriate Bank/Program change code, (And if required cc codes) then save it in the OAS database, thus it becomes just like selecting any on-board sound from the OAS database, and I can also do the same with Midi using the Midi Sound Banks)

Example: I have Kontakt setup in my host, (It could be any host) with Piano on program 001 & Guitar on program 030, from the arranger edit panel I just select the voice I want to change then select the voice I want to change it too from the VST Sound list (Self-Created) and the appropriate sound from the VST (Piano) for variation 1 is automatically selected, then for variation 4 I select the Guitar, I now save the style as a user style, and when I choose the style with variation 1 the VST Piano is automatically selected and played, and when I switch to Variation 4 the Guitar is automatically selected and played, there is no delay as the Multi has the sounds already loaded in.

Hope this helps

Bill