we call that a mouth harp where i'm from!
and yeah, i say umm and err alot in the tutorials. hehehehe... y'know how it is... the mind wanders, i'm usually thinking 5 steps ahead of where I am and whether or not there's maybe a better way to do something than the way i'm showing. plus, i warn you in the beginning of the first couple i posted that mine will not be even close to professional tutorials! hahahaha
on that note, i once watched a video tutorial i got from a 3dworld magazine long ago where the guy went without talking at one point for almost 5 minutes. you could hear traffic outside his window, and him taking drags off his cigarette. so, maybe we subconsciously say umm and err to remind the viewer that we haven't left them alone!
and song work with the jaw harp!
