What makes an "exotic" car sound the way it does?

Besides things like flatplane V8s, what gives exotics and other high-end cars their distinct, refined sounds? Is it cylinder count, displacement, something specific about the exhaust design? Like that guy that just posted a cold start in his Vanquish -- it just sounds so much better than if I were to stick an aftermarket exhaust on my car. It's not obnoxiously loud or droning, but when you punch it, it sounds so aggressive but somehow still smooth and refined. via /r/cars http://ift.tt/2rGrXiQ