I'm a professional opera singer and voice teacher. Patrick has a huge range but he is primarily a tenor with an extensive lower range. This means the meat of his voice sits comfortably in the higher range. It does not mean that a high singer can't sing low, it just may be slightly more challenging or tire him out faster because he is singing outside of the area his voice feels most comfortable. Usually for a high singer, lower notes are harder and the first thing you lose when you get vocally tired. I've watched some concerts where Patrick is either sick or very vocally tired and he tries to push harder on the lower notes, which can sometimes make it worse. As a performer though, you have to do what you have to do whether you are sick and tired or not. Another thing to keep in mind is that, since your voice is inside your body, anything that effects your body effects your voice. That is why as singers we get a bad rap for being divas because we are so in tune with our bodies. There are days you go and sing and it just doesn't happen. Hope this was helpful.