Gig Performer has a global transpose parameter, normally set to zero.
You can of course manually adjust the global transpose by clicking on it and entering a new transpose value directly or by using the UP/DOWN arrows to increment/decrement respectively the global transpose value. The new value will be applied to instruments in every rackspace except for those that you have explicitly configured to ignore the global transpose, typically for drum synths and effects that should be immune to global transpose.
Click here to read the complete article: https://gigperformer.com/controlling-the-global-transpose-from-your-keyboard/