I was just thinking about your 12-tet experiment, and I just realized, how would people with relative pitch deal with this? If they just hopped around "perfect" intervals they would slowly get out of tune with the original key. So do you almost have to somehow temper your notes as you sing / play them? Or do people just do that automatically? Sorry if my question makes no sense.
when you sing you gravitate toward where the pitch emotionally wants to be. which may be any combination of its relations to other notes, and/or other factors such as outer space